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The ability to assemble artificial systems that mimic aspects of natural light‐harvesting functions is fascinating and attractive for materials design. Given the complexity of such a system, a simple design pathway is desirable. Here, we argue that associative phase separation of oppositely charged conjugated polyelectrolytes (CPEs) can provide such a path in an environmentally benign medium: water. We find that complexation between an exciton–donor and acceptor CPE leads to formation of a complex fluid. We interrogate exciton transfer from the donor to the acceptor CPE within the complex fluid and find that transfer is highly efficient. We also find that excess molecular ions can tune the modulus of the inter‐CPE complex fluid. Even at high ion concentrations, CPEs remain complexed with significantly delocalized electronic wavefunctions. Our work lays the rational foundation for complex, tunable aqueous light‐harvesting systems via the intrinsic thermodynamics of associative phase separation. [ABSTRACT FROM AUTHOR]

A theory is presented for the upper bound on the mean time τ to the detection of an undersea acoustic communications network by an energy detector whose initial position and heading are uniformly distributed random variables. The network is an infinite square grid of omnidirectional transmit-receive nodes on a flat bottom. Each node transmits to one nearest neighbor at a bit-rate R equal to Shannon’s capacity, maximizing τ. The network sets a signaling bandwidth W and node-spacing D. The detector sets a false-alarm rate, integration time, height above the bottom, and speed. For W=5 kHz and D=1 km, τ is computed as a function of R in 200 -m water with propagation varying from spherical to cylindrical spreading, volume absorption of 2 dB per km (corresponding approximately to 15 kHz), and illustrative values for other parameters. [ABSTRACT FROM AUTHOR]

We report detailed Knight-shift measurements of the two indium sites in the heavy-fermion compound CeIrIn5 as a function of temperature and field orientation. We find that the Knight-shift anomaly is orientation dependent, with a crossover temperature T* that varies by 50% as the field is rotated from (001) to (100). This result suggests that the hybridization between the Ce 4f states and the itinerant conduction electrons is anisotropic, a result that reflects its collective origin, and may lead to anisotropic Kondo liquid behavior and unconventional superconductivity. [ABSTRACT FROM AUTHOR]

Na4Ir3O8 is a unique case of a hyperkagome 3D comer sharing triangular lattice that can be decorated with quantum spins. It has spurred a lot of theoretical interest as a spin liquid candidate. We present a comprehensive set of NMR data taken on both the 23Na and 17O sites. We show that disordered magnetic freezing of all Ir sites sets in below Tf ∼ 7 K, well below J = 300 K, with a drastic slowing down of fluctuations to a static state revealed by our T1 measurements. Above typically 2Tf, physical properties are relevant to the spin liquid state induced by this exotic geometry. While the shift data show that the susceptibility levels off below 80 K, 1 /T1 has little variation from 300 K to 2Tf. We discuss the implication of our results in the context of published experimental and theoretical work. [ABSTRACT FROM AUTHOR]

We report nuclear magnetic resonance Knight shift data in the heavy-fermion material CeIrIn5 at fields up to 30 T. The Knight shift of the In displays a strong anomaly, and we analyze the results using two interpretations. We find that the Kondo lattice coherence temperature and the effective mass of the heavy electrons remain largely unaffected by the magnetic field, despite the fact that the Zeeman energy is of the order of the coherence temperature. [ABSTRACT FROM AUTHOR]

The electric field gradient (EFG) at the As nuclei in the BaFe2As2 and SrFe2As2 iron arsenide compounds becomes axially asymmetric in the low temperature orthorhombic phase, but little has been reported about the EFG in the CaFe2As2 analog. We present As nuclear magnetic resonance (NMR) spectra as a function of orientation in this phase and extract the EFG tensor. The EFG asymmetry is significantly less in this material, which is a result of the unusually strong c-axis hybridization. [ABSTRACT FROM AUTHOR]

We present 75As nuclear magnetic resonance data in the paramagnetic and magnetic states of single-crystal CaFe2As2. The electric field gradient and the internal magnetic field at the As sites change discontinuously below the first-order structural transition at T0 = 169 K. In the magnetic state, we find a single value of the internal hyperfine field consistent with commensurate antiferromagnetic order of Fe moments pointing in the ab plane. The spin lattice relaxation rate shows Korringa behavior for T ≲ T0/3, reflecting the metallic nature of the ordered state. Surprisingly, T1-1 exhibits a small peak at 10 K, revealing the presence of slow spin fluctuations that may be associated with domain wall motion. [ABSTRACT FROM AUTHOR]

Given the link between neurotoxicity and exposure to pollutants, the potential behavioral neurotoxicity of benzo(a)pyrene [B(a)P] was investigated. Studies have established that B(a)P requires metabolic activation to highly reactive species to elicit many of its adverse effects. This study investigated the perturbation of nervous system function by correlating behavioral changes with the metabolism of B(a)P, antioxidant enzyme levels and lipid peroxidation in selected brain regions. The neurobehavioral effects of single oral doses of B(a)P (25-200 mg kg−1 body weight) on motor activity were examined in male F-344 rats at 2, 4, 6, 12, 24, 48, 72 and 96 h post treatment. Parent B(a)P and metabolites were measured at the above mentioned time points by reverse phase HPLC. The activity of several antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) and levels of malondialdehyde were determined at 6 and 96 h in both the striatum and hippocampus of B(a)P exposed rats. Suppression of motor activity (up to 70%) reached a maximum at 6 h, but was reversible at 96 h in all dose groups. The kinetics of disposition data show a strong link between B(a)P metabolism and the onset and duration of behavioral effects. Benzo(a)pyrene caused a 15-70% inhibition in the activity of superoxide dismutase and glutathione peroxidase and an enhancement in catalase and lipid peroxidation (up to 68%) in the striatum and hippocampus at 6 and 96 h post treatment, respectively. These findings suggest that B(a)P-induced acute neurobehavioral toxicity may occur through oxidative stress due to inhibition of the brain antioxidant scavenging system. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Fluroanthene (FLA) is a nonalternant representative of polycyclic aromatic hydrocarbon (PAH) family of toxic chemicals that are widely distributed in the environment. The effects of single acute doses of FLA on locomotor activities and the functional observational battery (FOB) were investigated in 8-week-old male and female F-344 rats. FLA was dissolved in peanut oil and administered by oral gavage as single doses of 0, 100, 200 and 400 mg/kg. Immediately after dosing, animals were placed in activity cages and monitored for nocturnal locomotor activities at 2-hour intervals and for a total of 12 hours for 5 consecutive days post treatment. Significant ( p < .001) reductions in horizontal activity, total distance, stereotypy, and vertical activity were observed. Rats administered acute doses of FLA were also subjected to the functional observational battery (FOB) tests that were conducted at 0, 2, 4, 6, 12, 24, 48, 72 and 96 hours after FLA administration. FLA-exposed animals showed significant ( p < .05) dysfunction, including ataxia, decreased grip strengths, increased landing foot splay, loss of aerial righting, increased urination and defecation, and decreased responses to sensory stimuli in both sexes. Neurological deficits in the FOB peaked at 6 hours and lasted for 48 hours post treatment. Significant ( p < .05) gender-related differences were noted in behavioral end points, with male rats showing greater sensitivity to FLA administration than females, as evidenced by their greater mean severity scores in FOB parameters and lower motor activity counts. These findings suggest that FLA can produce behavioral toxicity in F-344 rats and that motor activity and the FOB may serve as end points for the detection of acute FLA toxicity. [ABSTRACT FROM AUTHOR]

Acoustic signals from three long-range (500-700 km) transmission paths in the Northeast Pacific were examined for multipath structures. Sound propagation along each path encountered both different sound-speed provinces and unique bathymetry which, together with the range differences, caused characteristic pulse arrival patterns at each hydrophone site. The receivers were all on a sloping bottom at depths between 1200 and 1400 m and the source depth was at 450 m in deep water. Ray-path arrivals were modeled using impulse, a new ray-theoretical impulse response code written by one of us (RCS). This code uses piecewise continuous cubic polynomials to fit the sound-speed profile and bathymetric profile, and Runge-Kutta methods to solve the ray equation of motion. It allows arbitrary ray density in launch angle, and identifies eigenrays by searching for rays whose depths bracket the receiver and which were adjacent at the source. Using this procedure, we were able to identify most of the major pulse arrivals observed at each of the recording sites. [ABSTRACT FROM AUTHOR]

We present a ray-trace numerical study of the effects of mesoscale structure on the group velocity (defined as the average horizontal ray speed) of deep-refracted acoustic signals using data from a large-scale, near synoptic survey of the thermal structure in the upper 800 m of the Northwest Pacific ocean reported by Emery et al. [W. J. Emery, T. J. Reid, J. A. de Santo, R. N. Baer, and J. P. Dugan, J. Acoust. Soc. Am. 66, 831-841 (1979)]. A representative sample of twelve sound speed profiles (SSPs) from the survey show maximum variation of 10 m/s in the group velocity of a ray with a given J value, J being the phase integral, and illustrate how particular features in the SSPs cause local maxima in the group velocity as a function of J. [ABSTRACT FROM AUTHOR]

Signal speeds (average horizontal ray velocities) are calculated on the basis of bathymetry and nine sound speed profiles (SSPs) for three great circle paths from shot detonation sites off Perth, Australia to receivers near Fernando de Noronha (14 552 km) and Bermuda (19 766 and 19 810 km). We use two signal speed algorithms, one a long-range ray-tracing code and the other an adiabatic invariant approximation (AIA) method, which assumes J = ∮ c-1 sin [variant_greek_theta] dz is constant for a given ray (where ∮ dz is an integral over one-ray cycle, c the local depth-dependent sound speed, [variant_greek_theta] the ray angle, and z the depth coordinate). Comparison with field measurements made 21 years ago shows that the ray-tracing and AIA methods, when applied to the same eigenrays, yield values averaging, respectively, 5.9±2.3 and 4.5±2.4 m/s below the observed values. The AIA method, however, yields values only 2.0±1.6 m/s below measurements when applied to rays vertexing just above the chief bathymetric obstructions near the Crozet and Kerguelen Islands. The specific reason for the offset is unclear, but this study shows AIA methods can be accurate for very general range-dependent SSPs. [ABSTRACT FROM AUTHOR]

The adiabatic invariance of the phase integral c-1 sin[variant_greek_theta] dz≡J leads to new analytic results for the average horizontal ray speed in constricting parabolic, Hirsch, and bilinear sound velocity profiles (SVPs). Theoretical predictions agree well with exact numerical raytracing solutions even for nonslowly varying SVPs, and show that the average ray speed may either increase or decrease in a contricting channel, depending on the SVP type. The adiabatic invariant approximation (AIA) appears to provide physical insight, an accuracy check for present range-dependent codes, and an alternative in some cases to long-range raytracing, for conditons typical of SOFAR propagation. We illustrate the latter point with an application of the AIA to a set of SVPs representative of the eastern North Pacific. [ABSTRACT FROM AUTHOR]

The simplest Klein-Gordon (KG) breather is a compacton on a string subject to the force of gravity in a frictionless V-shaped trough. Its dynamics, spectrum, and energy are discussed and it is compared to sine-Gordon breathers. A generalization of this problem consists of a charged string subject to the electrostatic force of two semi-infinite coplanar charged planes separated by a gap of constant width. For motion in the midplane between these planes, the string's displacement u (x, t) satisfies the nonlinear KG equation (∂t2 - ∂x2) u = - tan-1 u in dimensionless form. Simulations of this equation reveal long-lived, breatherlike states, or "pseudobreathers," which preserve shape and speed to high accuracy when Lorentz-transformed to simulate collisions. [ABSTRACT FROM AUTHOR]

Acoustic signals from three long-range (500-700 km) transmission paths in the Northeast Pacific were examined for multipath structure. Sound propagation along each path encountered both different sound-speed provinces and unique bathymetry which, together with the range differences, caused characteristic pulse arrival patterns at each hydrophone site. The receivers were all on a sloping bottom at depths between 1200 and 1400 m and the source depth was at 450 m in deep water. Raypath arrivals were modeled using IMPULSE, a new ray-theoretical impulse response code written by one of us (RCS). This code uses piecewise continuous cubic polynomials to fit the sound-speed profile and bathymetric profile, and Runge-Kutta methods to solve the ray equation of motion. It allows arbitrary ray density in launch angle, and identifies eigenrays by searching for rays whose depths bracket the receiver and which were adjacent at the source. Using this procedure, we were able to identify most of the major pulse arrivals observed at each of the recording sites. [ABSTRACT FROM AUTHOR]

Beamforming for an array typically requires array-element localization (AEL) to within one-tenth of a wavelength. Often it is impractical to install dedicated, large-bandwidth AEL transponders with an array. This paper presents an approach to AEL for fixed, bottom-mounted arrays without transponders. High-SNR signals from multiple near-field imploding lightbulbs and interpolated correlations allow a statistical reduction in the inherent uncertainty in arrival-time measurements imposed by the bandwidth of the sensors. The method is illustrated with an application to the SWSS (shallow-water sensor string) array offshore of San Diego, at depths from 180 to 200 m. [ABSTRACT FROM AUTHOR]

We present As75 nuclear magnetic resonance data from measurements of a series of Ba(Fe1−xCox)2As2 crystals with 0.00≤x≤0.075 that reveals the coexistence of frozen antiferromagnetic domains and superconductivity for 0.060≤x≤0.071. Although bulk probes reveal no long range antiferromagnetic order beyond x=0.06, we find that the local spin dynamics reveal no qualitative change across this transition. The characteristic domain sizes vary by more than an order of magnitude, reaching a maximum variation at x=0.06. This inhomogeneous glassy dynamics may be an intrinsic response to the competition between superconductivity and antiferromagnetism in this system. [ABSTRACT FROM AUTHOR]

The electric field gradient (EFG) at the As nuclei in the BaFe2As2 and SrFe2As2 iron arsenide compounds becomes axially asymmetric in the low temperature orthorhombic phase, but little has been reported about the EFG in the CaFe2As2 analog. We present As nuclear magnetic resonance (NMR) spectra as a function of orientation in this phase and extract the EFG tensor. The EFG asymmetry is significantly less in this material, which is a result of the unusually strong c-axis hybridization. [ABSTRACT FROM AUTHOR]

CePt2In7 is a heavy fermion system with an antiferromagnetic transition at TN = 5.2 K at ambient pressure. 195Pt Knight shift measurements reveal anomalous behavior below T* ~40 K. By comparing the susceptibility and Knight shift data, we extract the individual contributions of the local moments and the heavy electron components to the magnetic susceptibility. Our results confirm the scaling predictions of the standard model, but reveal a surprising result, namely, that below 14 K the hybridized quasiparticles begin to "relocalize," an important precursor to their joining the local moments in becoming antiferromagnetically ordered at TN. [ABSTRACT FROM AUTHOR]

The behavioral changes caused by benzo(a)pyrene (BaP), a polycyclic aromatic hydrocarbon (PAH) compound, were monitored, and also its metabolite levels in cerebellum and cortex were measured in BaP treated rats to see if any relationship existed between these two aspects. Rats were administered 0, 25, 50, 100, and 200 mg/kg of BaP in peanut oil by oral gavage. Plasma, and brain tissue (cerebellum and cortex) samples were collected at 0, 2, 4, 6, 12, 24, 48, 72 and 96 h post administration. Neurotoxic effects peaked at 2 h after dosing and lasted 48 h after dosing for all dose groups. The metabolite levels remained the same from 2 to 4 h, reached a peak at 6 h post gavage and showed a gradual decline returning to baseline levels at 72 h when the motor activity of treatment groups also returned to control levels, indicating recovery from the effects of BaP. A significant (P<0.05) correlation between neurotoxic effects and BaP plasma, and brain metabolite concentrations suggests that metabolism plays an important role in modulating the neurobehavioral effects of BaP. [Copyright &y& Elsevier]

We present magnetotransport and 209Bi nuclear magnetic resonance (NMR) data on a series of single crystals of Bi2Se3, Bi2Te2Se, and CuxBi2Se3 with varying carrier concentrationn. The Knight shift of the bulk nuclei is strongly correlated with the carrier concentration via a hyperfine coupling of 27 μeV, which may have important consequences for scattering of the protected surface states. Surprisingly we find that the NMR linewidths and the spin-lattice relaxation rate appear to be dominated by the presence of localized spins, which may be related to the presence of Se vacancies. [ABSTRACT FROM AUTHOR]

We report 17O NMR measurements in single crystals of overdoped Bi2Sr2CaCu2O8+δ with Tc = 82 K. We measure the full anisotropy of the planar oxygen Knight shift, electric field gradient, and spin-lattice-relaxation rate tensors, and show that the entire temperature dependence is determined by the suppression of the density of states in the pseudogap below T* ~ 94 K. The linewidth can be explained by a combination of magnetic and quadrupolar broadening as a result of an inhomogeneous distribution of local hole concentrations that is consistent with scanning tunneling microscopy measurements. This distribution is temperature independent, does not break C4 symmetry, and exhibits no change below T* or Tc. [ABSTRACT FROM AUTHOR]

We present 75As nuclear magnetic resonance data in the paramagnetic and magnetic states of single-crystal CaFe2As2. The electric field gradient and the internal magnetic field at the As sites change discontinuously below the first-order structural transition at T0 = 169 K. In the magnetic state, we find a single value of the internal hyperfine field consistent with commensurate antiferromagnetic order of Fe moments pointing in the ab plane. The spin lattice relaxation rate shows Korringa behavior for T ≲ T0/3, reflecting the metallic nature of the ordered state. Surprisingly, T1-1 exhibits a small peak at 10 K, revealing the presence of slow spin fluctuations that may be associated with domain wall motion. [ABSTRACT FROM AUTHOR]

Na&#95;{4}Ir&#95;{3}O&#95;{8} is a unique case of a hyperkagome 3D corner sharing triangular lattice that can be decorated with quantum spins. It has spurred a lot of theoretical interest as a spin liquid candidate. We present a comprehensive set of NMR data taken on both the ^{23}Na and ^{17}O sites. We show that disordered magnetic freezing of all Ir sites sets in below T&#95;{f}~7 K, well below J=300 K, with a drastic slowing down of fluctuations to a static state revealed by our T&#95;{1} measurements. Above typically 2T&#95;{f}, physical properties are relevant to the spin liquid state induced by this exotic geometry. While the shift data show that the susceptibility levels off below 80 K, 1/T&#95;{1} has little variation from 300 K to 2T&#95;{f}. We discuss the implication of our results in the context of published experimental and theoretical work.

We present 75As nuclear magnetic resonance data from measurements of a series of Ba(Fe(1-x)Co(x))2As2 crystals with 0.00≤x≤0.075 that reveals the coexistence of frozen antiferromagnetic domains and superconductivity for 0.060≤x≤0.071. Although bulk probes reveal no long range antiferromagnetic order beyond x=0.06, we find that the local spin dynamics reveal no qualitative change across this transition. The characteristic domain sizes vary by more than an order of magnitude, reaching a maximum variation at x=0.06. This inhomogeneous glassy dynamics may be an intrinsic response to the competition between superconductivity and antiferromagnetism in this system.