The Electrostatic Ion Beam Trap : a mass spectrometer of infinite mass range

We study the ions dynamics inside an Electrostatic Ion Beam Trap (EIBT) and show that the stability of the trapping is ruled by a Hill's equation. This unexpectedly demonstrates that an EIBT, in the reference frame of the ions works very similar to a quadrupole trap. The parallelism between these two kinds of traps is illustrated by comparing experimental and theoretical stability diagrams of the EIBT. The main difference with quadrupole traps is that the stability depends only on the ratio of the acceleration and trapping electrostatic potentials, not on the mass nor the charge of the ions. All kinds of ions can be trapped simultaneously and since parametric resonances are proportional to the square root of the charge/mass ratio the EIBT can be used as a mass spectrometer of infinite mass range

A comparison of techniques for measuring automatic retrieval in conceptual priming

The speeded response technique has provided pure estimates of automatic retrieval in perceptual memory tasks. The present study was designed to investigate whether pure automatic retrieval could also be evidenced in a conceptual task. Subjects were encouraged to generate category exemplars using strictly automatic retrieval by presenting practice trials that did not allow responding with previously studied items and by encouraging speed of responding. This speeded condition was compared to a baseline condition in which conscious retrieval was not possible and to an explicit condition in which conscious retrieval was required. Average RTs in the speeded condition were the same as those in the baseline condition and were faster than those of the explicit condition, supporting the use of an automatic retrieval strategy in the speeded group. Semantic study did not increase target completion rates for the speeded or implicit groups, but it did for the explicit group, suggesting that conscious, but not automatic retrieval benefits from semantic encoding. Estimates of automatic retrieval obtained using PDP formula were identical to automatic estimates obtained using target completion from the speeded group. The idea of using higher frequency target category exemplars in a future study to further clarify present findings is explored

List Composition Effects for Masked Semantic Primes: Evidence Inconsistent with Activation Accounts

Priming is the benefit that an event receives when its processing has been preceded by the processing of a related or identical event. Context effects on priming are evident when priming changes as a function of some feature of experimental trials. The most commonly explored context effect is that of relatedness proportion (RP), where it has often been shown that the magnitude of priming (semantic or repetition) is directly related to the proportion of related trials: Increasing the related trials results in greater priming. Although previously thought to depend on strategic processing, recent evidence of context effects from designs using masked primes and short stimulus onset asynchronies (SOAs; less than 250 ms) refutes this strategy view because it should not be possible to enact strategies in such brief intervals. In addition, such findings provide evidence against the dominant view that masked priming with short SOAs results from automatic spreading activation because automatic spreading activation should not be influenced by contextual factors. The current set of experiments was designed to provide converging evidence for the notion that episodic accounts may best account for priming by exploring whether differences in another context variable—list composition—would alter semantic priming in a lexical decision task (LDT) for masked, short SOA (67 ms) primes. In 3 experiments, list composition was manipulated by presenting experimental trials that contained either 3 prime types (nominally related, semantically related, or unrelated) or 2 prime types (semantically related or unrelated) in either a between-subjects design (Experiments 1 and 2) or a within-subject design (Experiment 3). List composition effects were found: Response times (RTs) to semantically related primes were associated with a response cost in the 3-Prime-Type condition but were associated with a response benefit (facilitation) in the 2-Prime-Type condition. Episodic accounts can best account for these results, whereby to best facilitate target identification, the cognitive system is biased to detect primes containing features that are most transfer appropriate with respect to targets

Shape in an Atom of Space: Exploring quantum geometry phenomenology

A phenomenology for the deep spatial geometry of loop quantum gravity is introduced. In the context of a simple model, an atom of space, it is shown how purely combinatorial structures can affect observations. The angle operator is used to develop a model of angular corrections to local, continuum flat-space 3-geometries. The physical effects involve neither breaking of local Lorentz invariance nor Planck scale suppression, but rather reply on only the combinatorics of SU(2) recoupling. Bhabha scattering is discussed as an example of how the effects might be observationally accessible.Comment: 14 pages, 7 figures; v2 references adde

Flat-top temperature tuning response in periodically-poled nonlinear crystals

Second harmonic generation via periodically-poled nonlinear materials offers an efficient means of generating high-quality visible light that would be otherwise unattainable with traditional laser sources. While this technology has the potential for implementation in many mass-industrial applications, temperature stability requirements of 0.1 deg.C can make packaging with a pump source problematic. Using our high fidelity poling technique we have achieved precise placement of poled domains in Lithium Niobate based on the resulting mathematical models. These initial devices provide more than 4 deg.C flat-top temperature stability, albeit with a corresponding loss in operational efficiency. Our aim is to implement improved designs in magnesium-doped Lithium Niobate for packaging with near-room temperature diode-based pump sources, as could be applied towards RGB TV and projector applications

Mechanical and Chemical Control of Smooth Cordgrass in Waillapa Bay, Washington

We evaluated four methods to control smooth cordgrass (Spartina alterniflora Loisel), hereafter spartina, in Willapa Bay, Washington: mowing, mowing plus herbicide combination, herbicide only for clones, and aerial application of herbicide for meadows. (PDF has 7 pages.

Towards Loop Quantization of Plane Gravitational Waves

The polarized Gowdy model in terms of Ashtekar-Barbero variables is further reduced by including the Killing equations for plane-fronted parallel gravitational waves with parallel rays. The resulting constraint algebra, including one constraint derived from the Killing equations in addition to the standard ones of General Relativity, are shown to form a set of first-class constraints. Using earlier work by Banerjee and Date the constraints are expressed in terms of classical quantities that have an operator equivalent in Loop Quantum Gravity, making space-times with pp-waves accessible to loop quantization techniques.Comment: 14 page

Neutralizing antibody response during acute and chronic hepatitis C virus infection

Little is known about the role of Abs in determining the outcome of hepatitis C virus (HCV) infection. By using infectious retroviral pseudotypes bearing HCV glycoproteins, we measured neutralizing Ab (nAb) responses during acute and chronic HCV infection. In seven acutely infected health care workers, only two developed a nAb response that failed to associate with viral clearance. In contrast, the majority of chronically infected patients had nAbs. To determine the kinetics of strain-specific and crossreactive nAb emergence, we studied patient H, the source of the prototype genotype 1a H77 HCV strain. An early weak nAb response, specific for the autologous virus, was detected at seroconversion. However, neutralization of heterologous viruses was detected only between 33 and 111 weeks of infection. We also examined the development of nAbs in 10 chimpanzees infected with H77 clonal virus. No nAb responses were detected in three animals that cleared virus, whereas strain-specific nAbs were detected in six of the seven chronically infected animals after approximately 50 weeks of infection. The delayed appearance of high titer crossreactive nAbs in chronically infected patients suggests that selective mechanism(s) may operate to prevent the appearance of these Abs during acute infection. The long-term persistence of these nAbs in chronically infected patients may regulate viral replication