19,874 research outputs found
Administrative Process Reform in a Discretionary Age: The Role of Social Consequences
The basic rulemaking procedures of the Administrative Procedure Act have remained intact for thirty-eight years, but now Congress is seriously considering reform of those generic rules. To evaluate the merits of these reform proposals, we must develop criteria against which to judge them. Although procedural reforms are commonly judged against the goals of fairness, accuracy, and procedural efficiency, Professors Schroeder and Magat argue that these are insufficient criteria to apply to administrative process reforms at a time when agencies possess substantial discretion in the rulemaking process. In such a context, procedures have an impact on society in ways not adequately evaluated by the traditional criteria. Discretion means that agencies may choose from a set of possible rules, none of which has been foreclosed by the enabling legislation of the agency. Procedures influence which choices the agency makes and, because these choices alter the regulations and restrictions under which society operates, they affect the social consequences of regulation. This article describes a model of participant behavior necessary to trace the effects of procedures on the social consequences of regulation, articulates a set of criteria to evaluate these social consequences, and then analyzes two frequently proposed generic reforms to the APA: mandatory regulatory impact analysis and oversight by the Office of Management and Budget
Isolation of viruses responsible for the demise of an Emiliania huxleyi bloom in the English Channel
This study used analytical flow cytometry (AFC) to monitor the abundance of phytoplankton, coccoliths, bacteria and viruses in a transect that crossed a high reflectance area in the western English Channel. The high reflectance area, observed by satellite, was caused by the demise of an Emiliania huxleyi bloom. Water samples were collected from depth profiles at four stations, one station outside and three stations inside the high reflectance area. Plots of transect data revealed very obvious differences between Station 1, outside, and Stations 2–4, inside the high reflectance area. Inside, concentrations of viruses were higher; E. huxleyi cells were lower; coccoliths were higher; bacteria were higher and virus:bacteria ratio was lower than at Station 1, outside the high reflectance area. This data can simply be interpreted as virus-induced lysis of E. huxleyi cells in the bloom causing large concentrations of coccoliths to detach, resulting in the high reflectance observed by satellite imagery. This interpretation was supported by the isolation of two viruses, EhV84 and EhV86, from the high reflectance area that lysed cultures of E. huxleyi host strain CCMP1516. Basic characterization revealed that they were lytic viruses approximately 170 nm–190 nm in diameter with an icosahedral symmetry. Taken together, transect and isolation data suggest that viruses were the major contributor to the demise of the E. huxleyi population in the high reflectance area. Close coupling between microalgae, bacteria and viruses contributed to a large organic carbon input. Consequent cycling influenced the succession of an E. huxleyi-dominated population to a more characteristic mixed summer phytoplankton community
Feedback in a cavity QED system for control of quantum beats
Conditional measurements on the undriven mode of a two-mode cavity QED system
prepare a coherent superposition of ground states which generate quantum beats.
The continuous system drive induces decoherence through the phase interruptions
from Rayleigh scattering, which manifests as a decrease of the beat amplitude
and an increase of the frequency of oscillation. We report recent experiments
that implement a simple feedback mechanism to protect the quantum beat. We
continuously drive the system until a photon is detected, heralding the
presence of a coherent superposition. We then turn off the drive and let the
superposition evolve in the dark, protecting it against decoherence. At a later
time we reinstate the drive to measure the amplitude, phase, and frequency of
the beats. The amplitude can increase by more than fifty percent, while the
frequency is unchanged by the feedback.Comment: 13 pages, 5 figures, ICAP 2012 23rd International Conference on
Atomic Physic
Flexible body dynamic stability for high performance aircraft
Dynamic equations which include the effects of unsteady aerodynamic forces and a flexible body structure were developed for a free flying high performance fighter aircraft. The linear and angular deformations are assumed to be small in the body reference frame, allowing the equations to be linearized in the deformation variables. Equations for total body dynamics and flexible body dynamics are formulated using the hybrid coordinate method and integrated in a state space format. A detailed finite element model of a generic high performance fighter aircraft is used to generate the mass and stiffness matrices. Unsteady aerodynamics are represented by a rational function approximation of the doublet lattice matrices. The equations simplify for the case of constant angular rate of the body reference frame, allowing the effect of roll rate to be studied by computing the eigenvalues of the system. It is found that the rigid body modes of the aircraft are greatly affected by introducing a constant roll rate, while the effect on the flexible modes is minimal for this configuration
AGAPETA ZOEGANA (L.) (LEPIDOPTERA: COCHYLIDAE), A SUITABLE PROSPECT FOR BIOLOGICAL CONTROL OF SPOTTED AND DIFFUSE KNAPWEED, CENTAUREA MACULOSA MONNET DE LA MARCK AND CENTAUREA DIFFUSA MONNET DE LA MARCK (COMPOSITAE) IN NORTH AMERICA
The taxonomy, distribution, life history, and host plant relationships of the cochylid moth Agapeta zoegana (L.), an oligophagous, facultatively multivoltine root feeder, are discussed. The results of oviposition and larval feeding tests with 56 plant species in five families are presented and show that A. zoegana is restricted to a few closely related species of Centaurea. In Europe the moth is widely distributed and abundant in the majority of the root-feeding guilds of Centaurea maculosa Monnet de la Marck studied, with densities of 23.6 larvae per 100 roots in eastern Austria/northwestern Hungary and less than 8 larvae per 100 roots in central Hungary and the Alsace. The acceptance of target North American species (the tetraploid form of C. maculosa and the diploid Centaurea diffusa Monnet de la Marck), the damage caused, and the active searching ability rate A. zoegana as a potentially effective natural enemy of spotted and diffuse knapweed in North America. Agapeta zoegana will be especially promising as it predominantly attacks the rosette, which is, according to a recently developed population model for diffuse knapweed in Canada, the most sensitive stage determining equilibrium knapweed density. Agapeta zoegana is compatible with Pelochrista medullana Staudinger (Lepidoptera: Cochylidae), another knapweed root feeder recently introduced into North America, and will complement the seed-feeding species already established. The moth was approved for release in Canada and the USA and has been established in British Columbia since 1984 on C. diffus
Vacancy complexes with oversized impurities in Si and Ge
In this paper we examine the electronic and geometrical structure of
impurity-vacancy complexes in Si and Ge. Already Watkins suggested that in Si
the pairing of Sn with the vacancy produces a complex with the Sn-atom at the
bond center and the vacancy split into two half vacancies on the neighboring
sites. Within the framework of density-functional theory we use two
complementary ab initio methods, the pseudopotential plane wave (PPW) method
and the all-electron Kohn-Korringa-Rostoker (KKR) method, to investigate the
structure of vacancy complexes with 11 different sp-impurities. For the case of
Sn in Si, we confirm the split configuration and obtain good agreement with EPR
data of Watkins. In general we find that all impurities of the 5sp and 6sp
series in Si and Ge prefer the split-vacancy configuration, with an energy gain
of 0.5 to 1 eV compared to the substitutional complex. On the other hand,
impurities of the 3sp and 4sp series form a (slightly distorted) substitutional
complex. Al impurities show an exception from this rule, forming a split
complex in Si and a strongly distorted substitutional complex in Ge. We find a
strong correlation of these data with the size of the isolated impurities,
being defined via the lattice relaxations of the nearest neighbors.Comment: 8 pages, 4 bw figure
An Interneuron Circuit Reproducing Essential Spectral Features of Field Potentials
This document is the Accepted Manuscript version of the following article: Reinoud Maex, ‘An Interneuron Circuit Reproducing Essential Spectral Features of Field Potentials’, Neural Computation, March 2018. Under embargo until 22 June 2018. The final, definitive version of this paper is available online at doi: https://doi.org/10.1162/NECO_a_01068. © 2018 Massachusetts Institute of Technology. Content in the UH Research Archive is made available for personal research, educational, and non-commercial purposes only. Unless otherwise stated, all content is protected by copyright, and in the absence of an open license, permissions for further re-use should be sought from the publisher, the author, or other copyright holder.Recent advances in engineering and signal processing have renewed the interest in invasive and surface brain recordings, yet many features of cortical field potentials remain incompletely understood. In the present computational study, we show that a model circuit of interneurons, coupled via both GABA(A) receptor synapses and electrical synapses, reproduces many essential features of the power spectrum of local field potential (LFP) recordings, such as 1/f power scaling at low frequency (< 10 Hz) , power accumulation in the γ-frequency band (30–100 Hz), and a robust α rhythm in the absence of stimulation. The low-frequency 1/f power scaling depends on strong reciprocal inhibition, whereas the α rhythm is generated by electrical coupling of intrinsically active neurons. As in previous studies, the γ power arises through the amplifica- tion of single-neuron spectral properties, owing to the refractory period, by parameters that favour neuronal synchrony, such as delayed inhibition. The present study also confirms that both synaptic and voltage-gated membrane currents substantially contribute to the LFP, and that high-frequency signals such as action potentials quickly taper off with distance. Given the ubiquity of electrically coupled interneuron circuits in the mammalian brain, they may be major determinants of the recorded potentials.Peer reviewe
Air hydrodynamics of the ultrafast laser-triggered spark gap
We present space and time resolved measurements of the air hydrodynamics
induced by ultrafast laser pulse excitation of the air gap between two
electrodes at high potential difference. We explore both plasma-based and
plasma-free gap excitation. The former uses the plasma left in the wake of
femtosecond filamentation, while the latter exploits air heating by
multiple-pulse resonant excitation of quantum molecular wavepackets. We find
that the cumulative electrode-driven air density depression channel initiated
by the laser plays the dominant role in the gap evolution leading to breakdown
- …