Showing papers by "Chalk River Laboratories published in 2013"
TL;DR: It is found that liquid domain size increases with the extent of acyl chain unsaturation (DOPC:POPC ratio), and a direct correlation between domain size and the mismatch in bilayer thickness of the coexisting liquid-ordered and liquid-disordered phases is found, suggesting a dominant role for line tension in controlling domain size.
145 citations
TL;DR: In this article, the authors showed evidence of an antioxidant mechanism for vitamin E which correlates strongly with its physical location in a model lipid bilayer, and they combined data from neutron diffraction, NMR, and UV spectroscopy experiments all suggest that reduction of reactive oxygen species and lipid radicals occurs specifically at the membrane's hydrophobic-hydrophilic interface.
Abstract: We show evidence of an antioxidant mechanism for vitamin E which correlates strongly with its physical location in a model lipid bilayer. These data address the overlooked problem of the physical distance between the vitamin’s reducing hydrogen and lipid acyl chain radicals. Our combined data from neutron diffraction, NMR, and UV spectroscopy experiments all suggest that reduction of reactive oxygen species and lipid radicals occurs specifically at the membrane’s hydrophobic–hydrophilic interface. The latter is possible when the acyl chain “snorkels” to the interface from the hydrocarbon matrix. Moreover, not all model lipids are equal in this regard, as indicated by the small differences in vitamin’s location. The present result is a clear example of the importance of lipid diversity in controlling the dynamic structural properties of biological membranes. Importantly, our results suggest that measurements of aToc oxidation kinetics, and its products, should be revisited by taking into consideration the ...
119 citations
TL;DR: It is shown that longitudinal optic phonon modes carry the largest amount of heat, in contrast to past simulations and that the total conductivity demonstrates a quantitative correspondence between microscopic and macroscopic phonon physics.
Abstract: Inelastic neutron scattering measurements of individual phonon lifetimes and dispersion at 295 and 1200 K have been used to probe anharmonicity and thermal conductivity in UO2 They show that longitudinal optic phonon modes carry the largest amount of heat, in contrast to past simulations and that the total conductivity demonstrates a quantitative correspondence between microscopic and macroscopic phonon physics We have further performed first-principles simulations for UO2 showing semiquantitative agreement with phonon lifetimes at 295 K, but larger anharmonicity than measured at 1200 K
115 citations
TL;DR: Evidence is presented for the existence of highly ordered lipid domains in the cholesterol-rich (32.5 mol%) liquid-ordered phase of dipalmitoylphosphatidylcholine membranes, which implies non-uniform distribution of cholesterol between the two phases.
Abstract: Rafts, or functional domains, are transient nano- or mesoscopic structures in the exoplasmic leaflet of the plasma membrane, and are thought to be essential for many cellular processes. Using neutron diffraction and computer modelling, we present evidence for the existence of highly ordered lipid domains in the cholesterol-rich (32.5 mol%) liquid-ordered ([Formula: see text]) phase of dipalmitoylphosphatidylcholine membranes. The liquid ordered phase in one-component lipid membranes has previously been thought to be a homogeneous phase. The presence of highly ordered lipid domains embedded in a disordered lipid matrix implies non-uniform distribution of cholesterol between the two phases. The experimental results are in excellent agreement with recent computer simulations of DPPC/cholesterol complexes [Meinhardt, Vink and Schmid (2013). Proc Natl Acad Sci USA 110(12): 4476-4481], which reported the existence of nanometer size [Formula: see text] domains in a liquid disordered lipid environment.
104 citations
TL;DR: The relationship between OBT speciation and the OBT/HTO ratio in environmental samples will be useful in this regard, providing information on the previous tritium exposure conditions in the environment and the currenttritium dynamics.
94 citations
TL;DR: In this article, a comparison between the theoretical results and the PNR and magnetometry data shows that finite-size effects confine the wavelength and lead to a quantization of the number of turns in the helicoid.
Abstract: Magnetoresistance (MR), polarized neutron reflectometry (PNR), and magnetometry measurements in MnSi thin films and rigorous analytical solutions of the micromagnetic equations show that the field-induced unwinding of confined helicoids occurs via discrete steps. A comparison between the theoretical results and the PNR and magnetometry data shows that finite-size effects confine the wavelength and lead to a quantization of the number of turns in the helicoid. We demonstrate that the magnetic state of these finite helicoids can be read by electrical means.
91 citations
TL;DR: Melatonin decreases the thickness of both model membranes by disordering the lipid hydrocarbon chains, thus increasing membrane fluidity, in stark contrast to the much accepted ordering effect induced by cholesterol, which causes membranes to thicken.
88 citations
TL;DR: In this paper, the magnetic and structural phase behaviors of the single-layer Mott insulating iridate Sr${}{2}$IrO${}_{4}$ were investigated and compared with the bilayer bilayer iridate, where both materials exhibit magnetic domains originating from crystallographic twinning and comparable moment sizes.
Abstract: Neutron diffraction measurements exploring the magnetic and structural phase behaviors of the candidate ${J}_{\mathrm{eff}}=1/2$ Mott insulating iridate Sr${}_{2}$IrO${}_{4}$ are presented. Comparisons are drawn between the correlated magnetism in this single-layer system and its bilayer analog Sr${}_{3}$Ir${}_{2}$O${}_{7}$, where both materials exhibit magnetic domains originating from crystallographic twinning and comparable moment sizes. Weakly temperature-dependent superlattice peaks violating the reported tetragonal space group of Sr${}_{2}$IrO${}_{4}$ are observed, supporting the notion of a lower structural symmetry arising from a high-temperature lattice distortion, and we use this to argue that moments orient along a unique in-plane axis demonstrating an orthorhombic symmetry in the resulting spin structure. Our results demonstrate that the correlated spin order and structural phase behaviors in both single-layer and bilayer Sr${}_{n+1}$Ir${}_{n}$O${}_{3n+1}$ systems are remarkably similar and suggest comparable correlation strengths in each system.
81 citations
TL;DR: In this paper, the authors proposed that lipid domains and so-called "rafts" characterized by high local levels of cholesterol in a liquid-ordered phase are important for a wide range of cellular functions and their types of ordering have become urgent.
Abstract: Cholesterol is the single most abundant molecule in animal plasma membranes, in the range of 20–30 mol%, where it is known to modulate the lipid-bilayer component of the membrane and lead to increased mechanical stability, lower permeability, larger thickness, and a distinct lateral organization. The phase equilibria of membranes with cholesterol and the associated large- and small-scale structure have turned out to be a particularly elusive problem. With the proposal that lipid domains and so-called ‘rafts’, characterized by high local levels of cholesterol in a liquid-ordered phase, are important for a wide range of cellular functions, an understanding and a quantitative assessment of the nature of these cholesterol-induced structures and their types of ordering have become urgent. Recent progress in neutron diffraction studies of lipid–cholesterol model membranes has now revealed details of the lateral ordering, and combined with earlier molecular model studies a picture emerges of the membrane as a locally structured liquid with small ordered ‘domains’ of a highly dynamic nature.
69 citations
TL;DR: The development of the Cu-Cl cycle has been pursued by several countries within the framework of the Generation IV International Forum (GIF) for hydrogen production with the next generation of nuclear reactors as discussed by the authors.
62 citations
TL;DR: The results imply an avoided quantum critical point, which is expected to strongly influence the properties of both the normal and superconducting states.
Abstract: We study the structural and magnetic orders in electron-doped BaFe2-xNixAs2 by high-resolution synchrotron x-ray and neutron scatterings. Upon Ni doping x, the nearly simultaneous tetragonal-to-orthorhombic structural (T-s) and antiferromagnetic (T-N) phase transitions in BaFe2As2 are gradually suppressed and separated, resulting in T-s > T-N with increasing x, as was previously observed. However, the temperature separation between T-s and T-N decreases with increasing x for x >= 0.065, tending toward a quantum bicritical point near optimal superconductivity at x approximate to 0.1. The zero-temperature transition is preempted by the formation of a secondary incommensurate magnetic phase in the region 0: 088 less than or similar to x less than or similar to 0.104, resulting in a finite value of T-N approximate to T-c + 10 K above the superconducting dome around x approximate to 0.1. Our results imply an avoided quantum critical point, which is expected to strongly influence the properties of both the normal and superconducting states.
TL;DR: X-ray scattering was used to investigate 5′-adenosine monophosphate (AMP) molecules captured in a multilamellar phospholipid matrix composed of dimyristoylphosphatidylcholine and found that instead of forming a random array, the AMP molecules are highly entangled, with the phosphate and ribose groups in close proximity, which may facilitate polymerization of the nucleotides into RNA-like polymers.
Abstract: A fundamental question of biology is how nucleic acids first assembled and then were incorporated into the earliest forms of cellular life 4 billion years ago. The polymerization of nucleotides is a condensation reaction in which phosphodiester bonds are formed. This reaction cannot occur in aqueous solutions, but guided polymerization in an anhydrous lipid environment could promote a non-enzymatic condensation reaction in which oligomers of single stranded nucleic acids are synthesized. We used X-ray scattering to investigate 5′-adenosine monophosphate (AMP) molecules captured in a multilamellar phospholipid matrix composed of dimyristoylphosphatidylcholine. Bragg peaks corresponding to the lateral organization of the confined AMP molecules were observed. Instead of forming a random array, the AMP molecules are highly entangled, with the phosphate and ribose groups in close proximity. This structure may facilitate polymerization of the nucleotides into RNA-like polymers.
TL;DR: In this article, the molecular in-plane and out-of-plane structure of DMPC membranes containing up to 60 mol% of cholesterol was studied using X-ray diffraction.
Abstract: The molecular in-plane and out-of-plane structure of dimyristoylphosphatidylcholine (DMPC) membranes containing up to 60 mol% of cholesterol was studied using X-ray diffraction. Up to 37.5 mol% cholesterol could be dissolved in the membranes, resulting in a disordered lateral membrane structure. Highly ordered cholesterol structures were observed at cholesterol concentrations of more than 40 mol% cholesterol. These structures were characterized as immiscible cholesterol plaques, i.e., bilayers of cholesterol molecules coexisting with the lipid bilayer. The cholesterol molecules were found to form a monoclinic structure at 40 mol% cholesterol, which transformed into a triclinic arrangement at the highest concentration of 60 mol%. Monoclinic and triclinic structures were found to coexist at cholesterol concentrations between 50 and 55 mol%.
TL;DR: The results show that quasiparticles in a system hitherto thought of as "classical" can indeed break down, and all three key features of the nonlinear effects as theoretically predicted are observed, in the inelastic neutron scattering measurements of single crystal LuMnO3.
Abstract: The breakdown of magnons, the quasiparticles of magnetic systems, has rarely been seen. By using an inelastic neutron scattering technique, we report the observation of spontaneous magnon decay in multiferroic ${\mathrm{LuMnO}}_{3}$, a simple two dimensional Heisenberg triangular lattice antiferromagnet, with large spin $S=2$. The origin of this rare phenomenon lies in the nonvanishing cubic interaction between magnons in the spin Hamiltonian arising from the noncollinear 120\ifmmode^\circ\else\textdegree\fi{} spin structure. We observed all three key features of the nonlinear effects as theoretically predicted: a rotonlike minimum, a flat mode, and a linewidth broadening, in our inelastic neutron scattering measurements of single crystal ${\mathrm{LuMnO}}_{3}$. Our results show that quasiparticles in a system hitherto thought of as ``classical'' can indeed break down.
TL;DR: In this article, heavy ion irradiations were performed while observing the damage evolution using an intermediate voltage electron microscope (IVEM) operating at 200kV. The number density of the defects consisted mostly of stacking fault tetrahedras (SFTs), 1/2 perfect loops and small 1/3 faulted Frank loops.
TL;DR: In this paper, the response of Cs2LiYCl6:Ce (CLYC) scintillator material to fast neutrons has been measured using a Van de Graaff accelerator.
Abstract: The response of Cs2LiYCl6:Ce (CLYC) scintillator material to fast neutrons has been measured using a Van de Graaff accelerator. Beams of monoenergetic neutrons in the energy range 0.359 MeV to 4.703 MeV were used to irradiate a 9 mm × 9.5 mm × 12 mm CLYC crystal. Following pulse-shape discrimination to separate neutron and gamma-ray events, peaks are observed in the neutron spectrum and assigned to fast-neutron events in the scintillator. One of the peaks is interpreted as being due to the 35Cl(n, p)35S reaction, and it is shown that the proton energy released in this reaction varies linearly with the energy of the incoming neutron. The linearity of the response may enable CLYC to be used for fast-neutron spectroscopy with well defined spectral peaks. The response of CLYC to thermal neutrons and gamma rays is well known, and the material has potential for simultaneous thermal-neutron detection, fast-neutron spectroscopy, and gamma-ray spectroscopy.
TL;DR: The percentage of the exchangeable OBT was determined to range from 20% to 57% and was found to depend on the type of vegetables as well as the sequence of the plants exposure to HTO.
TL;DR: In this article, the authors used inelastic neutron scattering (INS) spectroscopy to study the magnetic excitations spectra throughout the Brillouin zone in electron-doped iron pnictide superconductors BaFe2-xNixAs2 with x = 0.096, 0.15,0.18.
Abstract: We use inelastic neutron scattering (INS) spectroscopy to study the magnetic excitations spectra throughout the Brillouin zone in electron-doped iron pnictide superconductors BaFe2-xNixAs2 with x = 0.096,0.15,0.18. While the x = 0.096 sample is near optimal superconductivity with T-c = 20 K and has coexisting static incommensurate magnetic order, the x = 0.15,0.18 samples are electron overdoped with reduced T-c of 14 and 8 K, respectively, and have no static antiferromagnetic (AF) order. In previous INS work on undoped (x = 0) and electron optimally doped (x = 0.1) samples, the effect of electron doping was found to modify spin waves in the parent compound BaFe2As2 below similar to 100 meV and induce a neutron spin resonance at the commensurate AF ordering wave vector that couples with superconductivity. While the new data collected on the x = 0.096 sample confirm the overall features of the earlier work, our careful temperature dependent study of the resonance reveals that the resonance suddenly changes its Q width below T-c similar to that of the optimally hole-doped iron pnictides Ba0.67K0.33Fe2As2. In addition, we establish the dispersion of the resonance and find it to change from commensurate to transversely incommensurate with increasing energy. Upon further electron doping to overdoped iron pnictides with x = 0.15 and 0.18, the resonance becomes weaker and transversely incommensurate at all energies, while spin excitations above similar to 100 meV are still not much affected. Our absolute spin excitation intensity measurements throughout the Brillouin zone for x = 0.096,0.15,0.18 confirm the notion that the low-energy spin excitation coupling with itinerant electron is important for superconductivity in these materials, even though the high-energy spin excitations are weakly doping dependent.
TL;DR: In this article, an electric field between the bottom and the top electrode switches the ferroelectric domain state with concomitant changes in magnetic reflections observed with neutron diffraction, indicating changes in the antiferromagnetic domain populations.
Abstract: Direct evidence of controlling the population of magnetic domains in BiFeO${}_{3}$ thin films through electric field is reported using neutron diffraction. By fabricating BiFeO${}_{3}$ thin films on vicinal SrTiO${}_{3}$ substrates, we have achieved ferroelectric monodomains as confirmed by piezoresponse force microscopy. The application of an electric field between the bottom SrRuO${}_{3}$ and the top electrode switches the ferroelectric domain state with concomitant changes in magnetic reflections observed with neutron diffraction, indicating changes in the antiferromagnetic domain populations. The observed magnetoelectric switching behavior by neutron diffraction is compared with the electric-field effect on the magneto-optical Kerr effect measurement on patterned pads of exchange coupled Co film deposited on top of the BiFeO${}_{3}$ films. The present result shows possible new directions for the realization of magnetoelectric devices.
TL;DR: Several methods used to analyze the SANS signal arising from freely suspended unilamellar vesicles containing lateral heterogeneity are examined, including an analytical model for a single, round domain on a spherical vesicle and a numerical method that uses Monte Carlo simulation to describe systems with multiple domains and/or more complicated morphologies.
10 Jun 2013-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, in situ neutron diffraction has been used to examine the pseudoelastic behavior of an extruded Mg-8.5% Al alloy during twinning-dominated cyclic deformation in both tension and compression.
Abstract: In - situ neutron diffraction has been used to examine the pseudoelastic behavior of an extruded Mg–8.5 wt.% Al alloy during twinning-dominated cyclic deformation in both tension and compression. Twinning activity is effectively tracked through the intensity variations of the diffraction peaks for some grain orientations. The results suggest that a fundamental difference in the pseudoelastic behavior between tension and compression cyclic loadings might be due to reversible detwinning–retwinning observed only during cyclic compression.
TL;DR: Spontaneously forming structures of a system composed of dimyristoyl phosphatidylcholine (DMPC) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO) were studied and spontaneous structural diagrams of the zwitterionic and charged systems were constructed.
Abstract: Spontaneously forming structures of a system composed of dimyristoyl phosphatidylcholine (DMPC) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO) were studied by small-angle neutron scattering (SANS), 31P NMR, and stimulated echo (STE) pulsed field gradient (PFG) 1H NMR diffusion measurements. Charged lipid dimyristoyl phosphatidylglycerol (DMPG) was used to induce different surface charge densities. The structures adopted were investigated as a function of temperature and lipid concentration for samples with a constant molar ratio of long-chain to short-chain lipids (= 3). In the absence of DMPG, zwitterionic bicellar mixtures exhibited a phase transition from discoidal bicelles, or ribbons, to multilamellar vesicles either upon dilution or with increased temperature. CHAPSO-containing mixtures showed a higher thermal stability in morphology than DHPC-containing mixtures at the corresponding lipid concentrations. In the presence of DMPG, discoidal bicelles (or ribbons) were...
TL;DR: In this article, a destructive slitting method was used to measure the stress intensity factor profile associated with the residual stress field as a function of crack length and deformations of the cut surfaces were measured to determine a contour map of the residual stresses in the specimen prior to the cut.
Abstract: Neutron diffraction measurements have been performed to determine the full residual stress tensor along the expected crack path in an austenitic stainless steel (Esshete 1250) compact tension weld specimen. A destructive slitting method was then implemented on the same specimen to measure the stress intensity factor profile associated with the residual stress field as a function of crack length. Finally deformations of the cut surfaces were measured to determine a contour map of the residual stresses in the specimen prior to the cut. The distributions of transverse residual stress measured by the three techniques are in close agreement. A peak tensile stress in excess of 600 MPa was found to be associated with an electron beam weld used to attach an extension piece to the test sample, which had been extracted from a pipe manual metal arc butt weld. The neutron diffraction measurements show that exceptionally high residual stress triaxiality is present at crack depths likely to be used for creep crack growth testing and where a peak stress intensity factor of 35 MPa√m was measured (crack depth of 21 mm). The neutron diffraction measurements identified maximum values of shear stress in the order of 50 MPa and showed that the principal stress directions were aligned to within ~20° of the specimen orthogonal axes. Furthermore it was confirmed that measurement of strains by neutron diffraction in just the three specimen orthogonal directions would have been sufficient to provide a reasonably accurate characterisation of the stress state in welded CT specimens.
TL;DR: An international workshop was held in 2012 to gather the scientific community interested in organically bound tritium to share their experience and to establish a current state of knowledge as discussed by the authors, which aimed to improve skills concerning OBT determination, transfer and behaviour in the environment.
Abstract: Within the last ten years there has been increasing interest in tritium behaviour and distribution in the environment. This is based partly on empirical findings that tritium discharged mostly as HTO can become transformed into organic forms in environmental samples. An international workshop was convened in France in 2012 to gather the scientific community interested in organically bound tritium to share their experience and to establish a current state of knowledge. This paper summarises the outcome of the workshop, which aimed to improve skills concerning OBT (Organically Bound Tritium) determination, transfer and behaviour in the environment. In order to improve OBT measurement credibility, it was decided to conduct and promote OBT analysis through inter-laboratory exercises. This practice will reduce uncertainty in OBT analysis results, providing better OBT model validation data and public dose assessments.
TL;DR: In this article, deuterium absorption into sputter-coated titanium (Ti) film electrodes during cathodic polarization in heavy water was monitored using in-situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS).
Abstract: Hydrogen (deuterium) absorption into sputter-coated titanium (Ti) film electrodes during cathodic polarization in heavy water (D2O) was monitored using in-situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS). The scattering length density (SLD) of Ti metal increased with increasing cathodic polarization, due to the penetration of deuterium through the surface oxide and into the underlying metal. The rate of D absorption estimated from the NR data showed a pattern with four distinctive regions separated by potential boundaries between −0.35 and −0.4 VSCE and around ∼−0.6 VSCE. EIS results support division of thebehaviorintothesepotentialranges.HydrogenabsorptionbyTiwasobservedatpotentials <∼−0.35VSCE,wherethecapacitance and resistance of the TiO2 layer dramatically changed. At this point, the D content of the film quickly achieved a level of ∼900 ppm by weight (atom ratio D:Ti ∼ 0.04). Decreased absorption kinetics were observed over the potential region from ∼−0.40 VSCE to −0.6 VSCE, indicating that D absorption was controlled either by a diffusion process through the TiO2 layer or by the formation of blocking hydrides at the Ti/TiO2 interface, at the base of the defective locations in the oxide through which the hydrogen was entering. Significant increases in the current density and SLD of the Ti film at potentials more negative than −0.6 VSCE were assigned to widespread hydrogen absorption and TiHx growth within the metal. These observations are consistent with hydrogen ingress through the oxide film, probably via weak points containing electronic defects and disorder, such as grain boundaries and triple points, at potentials as mild as ∼−0.4 VSCE, and with hydrogen penetration through continuous, intact oxide via the previously published redox transformation mechanism, at potentials more negative than −0.6 VSCE. © 2013 The Electrochemical Society. [DOI: 10.1149/2.020309jes] All rights reserved.
TL;DR: In this paper, the authors used a self-assembled monolayer (SAM) of β-thioglucose (TG) molecules to ensure that the solid substrate surface was hydrophilic and measured the electrochemical properties of the bilayer by recording differential capacitance curves.
TL;DR: Although the low-T annealing of samples has only a marginal effect on the mean size of end-state ULVs, it does affect their polydispersity, which increases with increased T, presumably driven by the entropy of the system.
TL;DR: Secretory clusterin (sCLU), an extracellular molecular chaperone, induced by low doses of cytotoxic agents, clears cell debris and is a pro-survival bystander factor that abrogates TGFβ1 signaling and most likely promotes wound healing.
Abstract: Inadvertent mammalian tissue exposures to low doses of ionizing radiation (IR) after radiation accidents, remediation of radioactive-contaminated areas, space travel or a dirty bomb represent an interesting trauma to an organism. Possible low-dose IR-induced bystander effects could impact our evaluation of human health effects, as cells within tissue are not equally damaged after doses of IR ⩽10 cGy. To understand tissue responses after low IR doses, we generated a reporter system using the human clusterin promoter fused to firefly luciferase (hCLUp-Luc). Secretory clusterin (sCLU), an extracellular molecular chaperone, induced by low doses of cytotoxic agents, clears cell debris. Low-dose IR (⩾2 cGy) exposure induced hCLUp-Luc activity with peak levels at 96 h, consistent with endogenous sCLU levels. As doses increased (⩾1 Gy), sCLU induction amplitudes increased and time-to-peak response decreased. sCLU expression was stimulated by insulin-like growth factor-1, but suppressed by p53. Responses in transgenic hCLUp-Luc reporter mice after low IR doses showed that specific tissues (that is, colon, spleen, mammary, thymus and bone marrow) of female mice induced hCLUp-Luc activity more than male mice after whole body (⩾10 cGy) irradiation. Tissue-specific, non-linear dose- and time-responses of hCLUp-Luc and endogenous sCLU levels were noted. Colon maintained homeostatic balance after 10 cGy. Bone marrow responded with delayed, but prolonged and elevated expression. Intraperitoneal administration of α-transforming growth factor (TGF)β1 (1D11), but not control (13C4) antibodies, immediately following IR exposure abrogated CLU induction responses. Induction in vivo also correlated with Smad signaling by activated TGFβ1 after IR. Mechanistically, media with elevated sCLU levels suppressed signaling, blocked apoptosis and increased survival of TGFβ1-exposed tumor or normal cells. Thus, sCLU is a pro-survival bystander factor that abrogates TGFβ1 signaling and most likely promotes wound healing.
TL;DR: The results suggested that the OBT formation rate was slower when the fish were exposed to HTO compared to when the Fish were ingesting OBT, and indicated that OBT can bioaccumulate in fish tissues following OBT-spiked food exposure.
TL;DR: Inelastic neutron-scattering measurements on single crystals of the frustrated two-leg ladder were performed in this article, where the ground state was described as a spin liquid phase with no long-range order down to 6 K.
Abstract: We report detailed inelastic neutron-scattering measurements on single crystals of the frustrated two-leg ladder ${\text{BiCu}}_{2}{\text{PO}}_{6}$, whose ground state is described as a spin liquid phase with no long-range order down to 6 K. Two branches of steeply dispersing long-lived spin excitations are observed with excitation gaps of ${\ensuremath{\Delta}}_{1}=1.90(9)$ meV and ${\ensuremath{\Delta}}_{2}=3.95(8)$ meV. Significant frustrating next-nearest-neighbor interactions along the ladder leg drive the minimum of each excitation branch to incommensurate wave vectors ${\ensuremath{\zeta}}_{1}=0.574\ensuremath{\pi}$ and ${\ensuremath{\zeta}}_{2}=0.553\ensuremath{\pi}$ for the lower and upper energy branches, respectively. The temperature dependence of the excitation spectrum near the gap energy is consistent with thermal activation into singly and doubly degenerate excited states. The observed magnetic excitation spectrum as well as earlier thermodynamic data could be consistently explained by the presence of strong anisotropic interactions in the ground-state Hamiltonian.