426 research outputs found
Oxide Fiber Cathode Materials for Rechargeable Lithium Cells
LiCoO2 and LiNiO2 fibers have been investigated as alternatives to LiCoO2 and LiNiO2 powders used as lithium-intercalation compounds in cathodes of rechargeable lithium-ion electrochemical cells. In making such a cathode, LiCoO2 or LiNiO2 powder is mixed with a binder [e.g., poly(vinylidene fluoride)] and an electrically conductive additive (usually carbon) and the mixture is pressed to form a disk. The binder and conductive additive contribute weight and volume, reducing the specific energy and energy density, respectively. In contrast, LiCoO2 or LiNiO2 fibers can be pressed and sintered to form a cathode, without need for a binder or a conductive additive. The inter-grain contacts of the fibers are stronger and have fewer defects than do those of powder particles. These characteristics translate to increased flexibility and greater resilience on cycling and, consequently, to reduced loss of capacity from cycle to cycle. Moreover, in comparison with a powder-based cathode, a fiber-based cathode is expected to exhibit significantly greater ionic and electronic conduction along the axes of the fibers. Results of preliminary charge/discharge-cycling tests suggest that energy densities of LiCoO2- and LiNiO2-fiber cathodes are approximately double those of the corresponding powder-based cathodes
Anomalous Hall conductivity of clean Sr2RuO4 at finite temperatures
Building on previous work, we calculate the temperature- and
frequency-dependent {\it anomalous} Hall conductivity for the putative
multiband chiral superconductor \Sr using a simple microscopic two-orbital
model without impurities. A Hall effect arises in this system without the
application of an external magnetic field due to the time-reversal-symmetry
breaking chiral superconducting state. The anomalous Hall conductivity is
nonzero only when there is more than one superconducting order parameter,
involving inter- as well as intra-band Cooper pairing. We find that such a
multiband superconducting state gives rise to a distinctive resonance in the
frequency-dependence of the Hall conductivity at a frequency close to the
inter-orbital hopping energy scale that describes hopping between Ru
and orbitals. The detection of this feature, robust to temperature and
impurity effects in the superconducting phase, would thus constitute compelling
evidence in favour of a multiband origin of superconductivity in \Sr, with
strong superconductivity on the and bands. The temperature
dependence of the Hall conductivity and Kerr rotation angle are studied within
this model at the one-loop approximation.Comment: 14 pages, 8 figures. Invited submission, proceedings of M2S 2012.
Published versio
Genomics and Autism Spectrum Disorder (ASD)
Purpose: To understand the current state of the evidence regarding translation of genetics and genomics into nursing care of children with (ASD)
Nutrition Campaign Knowledge and Dietary Behavior in Middle School Students
Background and Purpose: Federal nutrition campaigns are designed to make dietary recommendations accessible but have not been extensively evaluated. This paper explores whether knowledge of nutrition campaigns is associated with dietary behavior among young adolescents. Methods: Cross-sectional survey data were collected from 4,773 middle school students in Southern California. Hierarchical logistic regression models were used to assess the association between dietary behaviors and nutrition campaign knowledge, controlling for gender and ethnicity. Results: Knowledge of the Fruit & VeggiesMore Matters campaign was associated with increased odds of high fruit and vegetable consumption, knowledge of the MyPlate campaign was associated with neither, and both were associated with increased odds of not consuming soda. Conclusion: Overall, low percentages of students demonstrated knowledge of nutrition campaigns, and knowledge was associated with some dietary behaviors. More research is needed to examine the impact of nutrition campaigns while also accounting for other psychosocial and environmental factors that may affect soda, fruit, and vegetable consumption
A Correlation Between Circumstellar Disks and Rotation in the Upper Scorpius OB Association
We present projected rotational velocities for 20 early-type (B8-A9) and 74
late-type (F2-M8) members of the ~5 Myr old Upper Scorpius OB Association
derived from high dispersion optical spectra obtained with the High Resolution
Echelle Spectrometer (HIRES) on Keck I and the Magellan Inamori Kyocera Echelle
(MIKE) on the Magellan Clay telescope. The spectroscopic sample is composed of
stars and brown dwarfs with infrared signatures of circumstellar disks, both
primordial and debris, and non-excess sources of comparable spectral type. We
merge projected rotational velocities, accretion diagnostics, and Spitzer Space
Telescope Infrared Array Camera (IRAC) and Multiband Imaging Photometer for
Spitzer (MIPS) 24 micron photometry to examine the relationship between
rotation and circumstellar disks. The rotational velocities are strongly
correlated with spectral type, a proxy for mass, such that the median vsini for
B8-A9 type stars is: 195(+/-)70 km/s, F2-K4: 37.8(+/-)7.4 km/s, K5-K9:
13.8(+21.3/-8.2) km/s, M0-M5: 16.52(+/-)5.3 km/s, and M5.5-M8: 17.72(+/-)8.1
km/s. We find with a probability of >0.99 that M-type stars and brown dwarfs
having infrared excess suggestive of circumstellar disks rotate more slowly
than their non-excess counterparts. A similar correlation is present among
F2-K9 type stars, but only at the ~97% confidence level. Among the early-type
(B8-A9) members, rotational velocities of the debris-disk and non-disk
populations are indistinguishable. Considering the late-type (F2-M8) stars and
brown dwarfs, we find a low fraction of slowly rotating, non-excess sources
relative to younger star forming regions, suggesting that most have spun up
following disk dissipation. The few late-type (F2-M5) debris disk sources,
which may be representative of stars that have recently dispersed their inner
disks, are evenly divided between slow and moderate rotators.Comment: 41 pages, 11 figures, accepted for publication in the Astrophysical
Journa
Homogeneous Subgroups of Young Children with Autism Improve Phenotypic Characterization in the Study to Explore Early Development
The objective of this study was to identify homogenous classes of young children with autism spectrum disorder (ASD) to improve phenotypic characterization. Children were enrolled in the Study to Explore Early Development between 2 and 5 years of age. 707 children were classified with ASD after a comprehensive evaluation with strict diagnostic algorithms. Four classes of children with ASD were identified from latent class analysis: mild language delay with cognitive rigidity, mild language and motor delay with dysregulation, general developmental delay, and significant developmental delay with repetitive motor behaviors. We conclude that a four-class phenotypic model of children with ASD best describes our data and improves phenotypic characterization of young children with ASD. Implications for screening, diagnosis, and research are discussed
Quantifying the habitat and zoogeomorphic capabilities of spawning European barbel Barbus barbus, a lithophilous cyprinid
Suitable gravel availability is critical for the spawning success of lithophilous fishes, including redd builders. Redd construction during spawning can alter substrate characteristics, thereby influencing hydraulic conditions and sediment transport, highlighting the importance of spawning as a zoogeomorphic activity. Here, interactions between redd‐building fish and their spawning environment were investigated for European barbel Barbus barbus with a comparative approach across three English rivers: Teme (western), Great Ouse (eastern) and Idle (central). Sediment characteristics of spawning habitats were similar across the rivers, including subsurface fine sediment (<2 mm) content (≈20% dry weight), but elevated subsurface silt content and coarser surface sediments were found in the river Teme. Water velocities were similar at spawning sites despite differences in channel width and depth. Redds were characterized by a pit and tailspill, with no differences in surface grain‐size characteristics between these and the surrounding riverbed, but with topographic alteration (dimensions and tailspill amplitude) in line with those of salmonids. Estimates of the fraction of the bed that spawning barbel were capable of moving exceeded 97% in all rivers. Estimated reproductive potential varied significantly between the rivers Idle and Teme (3,098 to 9,715 eggs/m2), which was largely due to differences in barbel lengths affecting fecundity. Larger barbel, capable of producing and depositing more eggs, but in more spatially extensive redds, meaning fewer redds per given surface area of riverbed. Predictions of barbel egg mortality based on sand content were low across both rivers. The effects of silt on barbel egg and larvae development are unknown, but the levels detected here would significantly impact salmon egg mortality. Similarities in fish length to redd area and the size of moveable grains by spawning barbel and salmon suggest they have similar geomorphic effects on sediments, although fine sediment tolerance is highly divergent
Soil sedimentology at Gusev Crater from Columbia Memorial Station to Winter Haven
A total of 3140 individual particles were examined in 31 soils along Spirit’s traverse. Their size, shape, and texture were quantified and classified. They represent a unique record of 3 years of sedimentologic exploration from landing to sol 1085 covering the Plains Unit to Winter Haven where Spirit spent the Martian winter of 2006. Samples in the Plains Unit and Columbia Hills appear as reflecting contrasting textural domains. One is heterogeneous, with a continuum of angular-to-round particles of fine sand to pebble sizes that are generally dust covered and locally cemented in place. The second shows the effect of a dominant and ongoing dynamic aeolian process that redistributes a uniform population of medium-size sand. The texture of particles observed in the samples at Gusev Crater results from volcanic, aeolian, impact, and water-related processes
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