The optical properties of the nanoscale neodymium ceramic cluster (THF)8Nd8O2Se2(SePh)16 (Nd8) and molecular (DME)2Nd(SC6F5)3 (Nd1) were studied by optical absorption, photoluminescence, and ...time-resolved spectroscopy. Both complexes exhibited emission characteristic of solid-state materials with bands centered at 927, 1078, 1360, and 1843 nm for Nd8 and 897, 1071, 1347, and 1824 nm for Nd1. The observed red-shift in the absorption and emission bands of Nd8 is attributed to the increased covalency and nephelauxetic effect. Using the calculated radiative decay time, the quantum efficiency of the 4F3/2 → 4I11/2 transition is calculated to be 16% in Nd8 and 9% in Nd1 with corresponding stimulated emission cross sections of 3.04 × 10-20 cm2 in Nd8 and 1.61 × 10-20 cm2 in Nd1 that are comparable to those of solid-state inorganic systems. This efficiency is the highest reported value for “molecular” neodymium compounds. This finding, along with the novel 1.8 μm emission, is attributed to the absence of direct Nd3+ coordination with fluorescence quenching vibrational groups such as hydrocarbon or hydroxide groups. The direct coordination of S, Se, and F accounts for the improved fluorescence spectral properties, because these heavy anions facilitate a low phonon energy host environment for neodymium. Monte Carlo simulation permitted analysis of energy transfer processes to show the primary source of fluorescence quenching. Cross relaxation is responsible for the quenching of the 4F3/2 → 4I15/2 emission whereas excitation migration quenches the 4F3/2 → 4I9/2 emission. These processes are mediated by a dipole−dipole interaction for Nd8 and a quadrupole−quadrupole interaction for Nd1.
Hypogeococcus pungens Granara de Willink, sensu stricto, is a serious pest of cacti in Puerto Rico threating many Caribbean islands. A classical biological control program for H. pungens was ...initiated for Puerto Rico in 2010 with a survey for natural enemies of H. pungens in its native range of Argentina. Biological differences were observed between populations of H. pungens sampled on Amaranthaceae and Cactaceae. Molecular studies suggested that H. pungens populations from different host plant families are likely a complex of species. Our objective was to study the biology of H. pungens sensu stricto on specimens collected in the same locality and host plant as the holotype Tucumán Province, Argentina; Alternanthera pungens Kunth (Amaranthaceae). We were interested in the reproductive biology of females, longevity and survival of adults, the effect of temperature on the development, and nymph performance (survival and development) on five Cactaceae species. We found that H. pungens s.s showed marked biological differences from the populations collected on Cactaceae and exported to Australia for the biological control of the cactus Harrisia spp. The main differences were the presence of deuterotoky parthenogenesis and the fact that H. pungens did not attack Cactaceae in the laboratory. Our results provide biological evidence that H. pungens is a species complex. We propose that the population introduced to Australia is neither Hypogeococcus festerianus Lizer y Trelles nor H. pungens, but an undescribed species with three circuli, and that the Hypogeococcus pest of cacti in Puerto Rico is not H. pungens.
In previous works, using the asymptotic homogenization method (AHM), analytical formulae have been obtained for all global elastic constants of a binary fiber composite with perfect interfaces. In ...many cases of interest the perfect interphase is not an adequate model and it is necessary to include in the analytical models one or more interphases separating the reinforcement inclusion phase from the host matrix phase. In this article, an extension of AHM to thermoelastic heterogeneous problems is given. A simple closed form of effective properties for a three-phase unidirectional transversely isotropic composite is presented. By using homogenization schemes for periodic media, the local problems are solved and effective thermoelastic properties moduli are determined. The method is based on the assumption that the scale ratio between the periodic cell and the whole composite tends to zero. New universal relations for the three-phase thermoelastic composite are found from the AHM. In order to analyze the interphase effect, the effective thermoelastic moduli are compared with some theoretical approaches and experimental results reported in the literature.
The first observation of exotic states with a new quark content ccus decaying to the J/Psi K+ final state is reported with high significance from an amplitude analysis of the B+-> J/ Psi phi K+ ...decay. The analysis is carried out using proton-proton collision data corresponding to a total integrated luminosity of 9 fb- 1 collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The most significant state, Z(cs)(4000)+, has a mass of 4003 +/- 6 (-14) (+4) MeV, a width of 131 +/- 15 +/- 26 MeV, and spin parity J(P) = 1(+), where the quoted uncertainties are statistical and systematic, respectively. A new 1(+) X(4685) state decaying to the J/Psi phi final state is also observed with high significance. In addition, the four previously reported J/Psi phi states are confirmed and two more exotic states, Z(cs) (4220) (+) and X(4630), are observed with significance exceeding 5 standard deviations.
We present the high-energy-neutrino follow-up observations of the first gravitational wave transient GW150914 observed by the Advanced LIGO detectors on September 14, 2015. We search for coincident ...neutrino candidates within the data recorded by the IceCube and Antares neutrino detectors. A possible joint detection could be used in targeted electromagnetic follow-up observations, given the significantly better angular resolution of neutrino events compared to gravitational waves. We find no neutrino candidates in both temporal and spatial coincidence with the gravitational wave event. Within + or -500s of the gravitational wave event, the number of neutrino candidates detected by IceCube and Antares were three and zero, respectively. This is consistent with the expected atmospheric background, and none of the neutrino candidates were directionally coincident with GW150914. We use this nondetection to constrain neutrino emission from the gravitational-wave event.
Results are presented from a semicoherent search for continuous gravitational waves from the brightest low-mass X-ray binary, Scorpius X-1, using data collected during the first Advanced LIGO ...observing run. The search combines a frequency domain matched filter (Bessel-weighted F-statistic) with a hidden Markov model to track wandering of the neutron star spin frequency. No evidence of gravitational waves is found in the frequency range 60–650 Hz. Frequentist 95% confidence strain upper limits, h095%=4.0×10−25, 8.3×10−25, and 3.0×10−25 for electromagnetically restricted source orientation, unknown polarization, and circular polarization, respectively, are reported at 106 Hz. They are ≤10 times higher than the theoretical torque-balance limit at 106 Hz.
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