Bright Flash Neutron Radiography at the McClellan Nuclear Research Reactor

AbstractThe University of California, Davis McClellan Nuclear Research Center (MNRC) operates a 2 MW TRIGATM reactor, which is currently the highest power TRIGATM reactor in the United States. The Center was originally build by the US Air Force to detect hidden defects in aircraft structures using neutron radiography; the Center can accommodate samples as large as 10.00 m long, 3.65 m high, and weighing up to 2,270kg.The MNRC reactor can be pulsed to 350 MW for about 30ms (FWHM). The combination of a short neutron pulse with a fast microchannel plate based neutron detector enables high-resolution flash neutron radiography to complement conventional neutron radiograph

Effects of implicit fear of failure on cognitive processing. A diffusion model analysis

Whereas previous studies suggest that individuals with high implicit fear of failure (FF) perform worse on various indicators of general performance, the underlying mechanisms of this effect have not yet been understood. In our experimental study, 280 participants worked on a binary color discrimination task. Half of the participants were frustrated by means of negative performance feedback, while the control group received mainly positive feedback. We employed a diffusion model analysis (Ratcliff in Psychol Rev 85(2):59-108, 1978) to disentangle the different components involved in the execution of the task. Results revealed that participants in the frustration condition adopted more conservative decision settings (threshold separation parameter of the diffusion model). Besides, high implicit FF was related to slow information accumulation (drift), and this relation was stronger in the frustration condition. Participants with higher FF further showed reduced learning rates during the task. Task related intrusive thoughts are discussed as mechanism for reduced performance of high FF individuals. We conclude that diffusion model analyses can contribute to a better understanding of the mechanisms underlying the effects of psychological motives. (DIPF/Orig.

Superconformal R-charges and dyon multiplicities in N=2 gauge theories

N=(2,2) theories in 1+1D exhibit a direct correspondence between the R-charges of chiral operators at a conformal point and the multiplicities of BPS kinks in a massive deformation, as shown by Cecotti and Vafa. We obtain an analogous relation in 3+1D for N=2 gauge theories that are massive perturbations of Argyres-Douglas fixed points, utilizing the geometric engineering approach to N=2 vacua within IIB string theory. In this case the scaling dimensions of a certain subset of chiral operators at the UV fixed point are related to the multiplicities of BPS dyons. When the Argyres-Douglas SCFT is realized at the root of a baryonic Higgs branch, this translation from 1+1D to 3+1D can be understood physically from the relation between the bulk dynamics and the N=(2,2) worldsheet dynamics of vortices in the baryonic Higgs phase. Under a relevant perturbation, the BPS kink multiplicity on the vortex worldsheet translates to that of the bulk dyonic states. The latter viewpoint suggests the 3+1D version of the Cecotti-Vafa relation may hold more generally, and simple tests provide evidence in favor of this for more generic choices of the baryonic root.Comment: 16 pages, 1 figur

Heterotic/type I duality, D-instantons and an N=2 AdS/CFT correspondence

D-instanton effects are studied for the IIB orientifold T^2/I\Omega(-1)^{F_L} of Sen using type I/heterotic duality. An exact one loop threshold calculation of t_8 \tr F^4 and t_8(\tr F^2)^2 terms for the heterotic string on T^2 with Wilson lines breaking SO(32) to SO(8)^4 is related to D-instanton induced terms in the worldvolume of D7 branes in the orientifold. Introducing D3 branes and using the AdS/CFT correspondence in this case, these terms are used to calculate Yang-Mills instanton contributions to four point functions of the large N_c limit of N=2 USp(2N_c) SYM with four fundamental and one antisymmetric tensor hypermultiplets.Comment: 25 pages, harvmac(b), one figure, v2: minor changes, version to appear in PR

New Symmetries of Supersymmetric Effective Lagrangians

We consider the structure of effective lagrangians describing the low-energy dynamics of supersymmetric theories in which a global symmetry $G$ is spontaneously broken to a subgroup $H$ while supersymmetry is unbroken. In accordance with the supersymmetric Goldstone theorem, these lagrangians contain Nambu--Goldstone superfields associated with a coset space $G^c / \hat{H}$, where $G^c$ is the complexification of $G$ and $\hat{H}$ is the largest subgroup of $G^c$ that leaves the order parameter invariant. The lagrangian may also contain additional light matter fields. To analyze the effective lagrangian for the matter fields, we first consider the case where the effective lagrangian is obtained by integrating out heavy modes at weak coupling (but including non-perturbative effects such as instantons). We show that the superpotential of the matter fields is $\hat{H}$ invariant, which can give rise to non-trivial relations among independent $H$-invariants in the superpotential. We also show that the Kahler potential of the matter fields can be restricted by a remnant of $\hat{H}$ symmetry. These results are non-perturbative and have a simple group-theoretic interpretation. When we relax the weak-coupling constraint, there appear to be additional possibilities for the action of $\hat{H}$ on the matter fields, hinting that the constraints imposed by $\hat{H}$ may be even richer in strongly coupled theories.Comment: 23 pages, plain Te

What do you (think you) need? Perceived vs. experienced effects of need fulfillment on well-being

We compared two approaches towards assessing inter-individual differences in the effect of satisfaction and frustration of basic needs (autonomy, competence, relatedness) on well-being: perceived need effects (beliefs about the effect of need fulfillment on one\u27s well-being) and experienced need effects (the within-person coupling of need fulfillment and well-being). In two studies (total N = 1281), participants reported perceived need effects in a multidimensional way. In Study 2, daily need fulfillment and affective well-being were additionally assessed (daily-diary study; ten days). Associations between perceived and experienced need effects were significant (albeit small) for all three frustration dimensions, but only for one satisfaction dimension (relatedness), suggesting that they capture different constructs and might be related to different outcomes. (DIPF/Orig.

The matrix factorisations of the D-model

The fundamental matrix factorisations of the D-model superpotential are found and identified with the boundary states of the corresponding conformal field theory. The analysis is performed for both GSO-projections. We also comment on the relation of this analysis to the theory of surface singularities and their orbifold description.Comment: 23 pages, LaTe

On the Zero-Slope Limit of the Compactified Closed Bosonic String

In the framework of the compactified closed bosonic string theory with the extra spatial coordinates being circular with radius $R$, we perform both the zero-slope limit and the $R \rightarrow 0$ limit of the tree scattering amplitude of four massless scalar particles. We explicitly show that this double limit leads to amplitudes involving scalars which interact through the exchange of a scalar, spin 1 and spin 2 particle. In particular, this latter case reproduces the same result obtained in linearized quantum gravity.Comment: 10 pages, LaTex file, DSF-T-43/9

The low energy expansion of the one-loop type II superstring amplitude

The one-loop four-graviton amplitude in either of the type II superstring theories is expanded in powers of the external momenta up to and including terms of order s^4 log s R^4, where R^4 denotes a specific contraction of four linearized Weyl tensors and s is a Mandelstam invariant. Terms in this series are obtained by integrating powers of the two-dimensional scalar field theory propagator over the toroidal world-sheet as well as the moduli of the torus. The values of these coefficients match expectations based on duality relations between string theory and eleven-dimensional supergravity.Comment: harvmac (b), 25 pages, 3 eps figures. v2: Factors of 2 corrected. Conclusion unchange

Orientifolds, Unoriented Instantons and Localization

We consider world-sheet instanton effects in N=1 string orientifolds of noncompact toric Calabi-Yau threefolds. We show that unoriented closed string topological amplitudes can be exactly computed using localization techniques for holomorphic maps with involution. Our results are in precise agreement with mirror symmetry and large N duality predictions.Comment: 25 pages, 10 figures, published version; v4: typos correcte