Genetic modifiers of cognitive maintenance among older adults.

ObjectiveIdentify genetic factors associated with cognitive maintenance in late life and assess their association with gray matter (GM) volume in brain networks affected in aging.MethodsWe conducted a genome-wide association study of ∼2.4 M markers to identify modifiers of cognitive trajectories in Caucasian participants (N = 7,328) from two population-based cohorts of non-demented elderly. Standardized measures of global cognitive function (z-scores) over 10 and 6 years were calculated among participants and mixed model regression was used to determine subject-specific cognitive slopes. "Cognitive maintenance" was defined as a change in slope of ≥ 0 and was compared with all cognitive decliners (slope < 0). In an independent cohort of cognitively normal older Caucasians adults (N = 122), top association findings were then used to create genetic scores to assess whether carrying more cognitive maintenance alleles was associated with greater GM volume in specific brain networks using voxel-based morphometry.ResultsThe most significant association was on chromosome 11 (rs7109806, P = 7.8 × 10(-8)) near RIC3. RIC3 modulates activity of α7 nicotinic acetylcholine receptors, which have been implicated in synaptic plasticity and beta-amyloid binding. In the neuroimaging cohort, carrying more cognitive maintenance alleles was associated with greater volume in the right executive control network (RECN; PFWE  = 0.01).ConclusionsThese findings suggest that there may be genetic loci that promote healthy cognitive aging and that they may do so by conferring robustness to GM in the RECN. Future work is required to validate top candidate genes such as RIC3 for involvement in cognitive maintenance

Finite-Size-Scaling at the Jamming Transition: Corrections to Scaling and the Correlation Length Critical Exponent

We carry out a finite size scaling analysis of the jamming transition in frictionless bi-disperse soft core disks in two dimensions. We consider two different jamming protocols: (i) quench from random initial positions, and (ii) quasistatic shearing. By considering the fraction of jammed states as a function of packing fraction for systems with different numbers of particles, we determine the spatial correlation length critical exponent $\nu\approx 1$, and show that corrections to scaling are crucial for analyzing the data. We show that earlier numerical results yielding $\nu<1$ are due to the improper neglect of these corrections.Comment: 5 pages, 4 figures -- slightly revised version as accepted for Phys. Rev. E Rapid Communication

Salmon on the Brink: The Imperative of Integrating Environmental Standards and Review on an Ecosystem Scale

This Article examines the interplay between the Clean Water Act and Endangered Species Act, the necessity of applying these statutes under an ecosystem or watershed based model, and the need to coordinate and integrate standards and review processes under the acts. The concept of watershed management is summarized in Part II, and Part III gives a brief overview of the two statutes and their implementation. Part IV focuses on the opportunities for, and necessity of, streamlining and integrating the standards and review under the two statutes to support the integrated, place-based, management model envisioned by a watershed approach. We conclude in Part V that a change in the historical approach to environmental management is essential if we are to take the next big step forward in environmental health

Salmon on the Brink: The Imperative of Integrating Environmental Standards and Review on an Ecosystem Scale

This Article examines the interplay between the Clean Water Act and Endangered Species Act, the necessity of applying these statutes under an ecosystem or watershed based model, and the need to coordinate and integrate standards and review processes under the acts. The concept of watershed management is summarized in Part II, and Part III gives a brief overview of the two statutes and their implementation. Part IV focuses on the opportunities for, and necessity of, streamlining and integrating the standards and review under the two statutes to support the integrated, place-based, management model envisioned by a watershed approach. We conclude in Part V that a change in the historical approach to environmental management is essential if we are to take the next big step forward in environmental health

10 µm minority-carrier diffusion lengths in Si wires synthesized by Cu-catalyzed vapor-liquid-solid growth

The effective electron minority-carrier diffusion length, L_(n,eff), for 2.0 µm diameter Si wires that were synthesized by Cu-catalyzed vapor-liquid-solid growth was measured by scanning photocurrent microscopy. In dark, ambient conditions, L_(n,eff) was limited by surface recombination to a value of ≤ 0.7 µm. However, a value of L_(n,eff) = 10.5±1 µm was measured under broad-area illumination in low-level injection. The relatively long minority-carrier diffusion length observed under illumination is consistent with an increased surface passivation resulting from filling of the surface states of the Si wires by photogenerated carriers. These relatively large L_(n,eff) values have important implications for the design of high-efficiency, radial-junction photovoltaic cells from arrays of Si wires synthesized by metal-catalyzed growth processes

High-performance Si microwire photovoltaics

Crystalline Si wires, grown by the vapor–liquid–solid (VLS) process, have emerged as promising candidate materials for lowcost, thin-film photovoltaics. Here, we demonstrate VLS-grown Si microwires that have suitable electrical properties for high-performance photovoltaic applications, including long minority-carrier diffusion lengths (L_n » 30 µm) and low surface recombination velocities (S « 70 cm·s^(-1)). Single-wire radial p–n junction solar cells were fabricated with amorphous silicon and silicon nitride surface coatings, achieving up to 9.0% apparent photovoltaic efficiency, and exhibiting up to ~600 mV open-circuit voltage with over 80% fill factor. Projective single-wire measurements and optoelectronic simulations suggest that large-area Si wire-array solar cells have the potential to exceed 17% energy-conversion efficiency, offering a promising route toward cost-effective crystalline Si photovoltaics

Spatially Resolved Chandra HETG Spectroscopy of the NLR Ionization Cone in NGC 1068

We present initial results from a new 440-ks Chandra HETG GTO observation of the canonical Seyfert 2 galaxy NGC 1068. The proximity of NGC 1068, together with Chandra's superb spatial and spectral resolution, allow an unprecedented view of its nucleus and circumnuclear NLR. We perform the first spatially resolved high-resolution X-ray spectroscopy of the `ionization cone' in any AGN, and use the sensitive line diagnostics offered by the HETG to measure the ionization state, density, and temperature at discrete points along the ionized NLR. We argue that the NLR takes the form of outflowing photoionized gas, rather than gas that has been collisionally ionized by the small-scale radio jet in NGC 1068. We investigate evidence for any velocity gradients in the outflow, and describe our next steps in modeling the spatially resolved spectra as a function of distance from the nucleus.Comment: 5 pages, 2 figures, 1 video. To appear in refereed Proceedings of "X-ray Astronomy 2009: Present Status, Multi-Wavelength Approach and Future Perspectives", Bologna, Italy, September 7-11, 2009, AIP, eds. A. Comastri, M. Cappi, and L. Angelin

The Effect of Regulatory Intervention in Two-Sided Markets: An Assessment of Interchange-Fee Capping in Australia

The Reserve Bank of Australia reduced interchange fees by almost half thereby eliminating a significant source of revenue to issuers of credit cards. The purpose of this intervention was to align the prices of using various payment instruments with their social costs and thus reduce the use of cards, which the RBA viewed as a socially less efficient payment method than cash, checks, and PIN debit cards. The short-run result of this regulatory intervention has been the following: (1) Bank issuers have increased the fixed prices for cards and thereby recovered between 30 and 40 percent of the loss of interchange fee revenue; this fraction is likely to increase over time as cards renew and new solicitations go out. Bank issuers have not changed the per-transaction fees for cards much. (2) Merchants experienced a very small reduction in their costs. Both theory and limited empirical evidence suggest that the highly concentrated merchant sector in Australia has captured the reduction in interchange fees as profits and has not passed it on in the form of lower consumer prices. (3) The per-transaction price at the point of sale has not changed significantly. Merchants have not generally availed themselves of their right to surcharge card transactions and the per-transaction price faced by consumers from their card issuers has not changed much. Holding the number of cards fixed, the regulatory intervention has not altered prices in a way that could achieve the intent of the intervention. (4) There is relatively little evidence thus far that the intervention has in fact affected the volume of card transactions in Australia as intended by the regulation. (5) In the short-run, the effect of the regulation has been to transfer significant profits to the Australian merchant sector with that transfer being borne partly by bank issuers and partly by cardholders. (6) Since proprietary systems such as American Express were not subject to the pricing regulations and since American Express can enter into deals with banks to issue cards, banks have shifted volume from the regulated association systems to the unregulated proprietary systems.

Photoelectrochemical Hydrogen Evolution Using Si Microwire Arrays

Arrays of B-doped p-Si microwires, diffusion-doped with P to form a radial n+ emitter and subsequently coated with a 1.5-nm-thick discontinuous film of evaporated Pt, were used as photocathodes for H_2 evolution from water. These electrodes yielded thermodynamically based energy-conversion efficiencies >5% under 1 sun solar simulation, despite absorbing less than 50% of the above-band-gap incident photons. Analogous p-Si wire-array electrodes yielded efficiencies <0.2%, largely limited by the low photovoltage generated at the p-Si/H_2O junction