915 research outputs found
Poor performance of mutual funds in Spain. 1991-2007
Over the past 10 and 16 years, the average return on mutual funds in Spain was lower than the average return on government bonds at any term. Over the past 10 years, the average return on the funds was lower than inflation. In spite of these results, on December 31, 2007, 8,264,240 investors held 238.7 billion euros in the 2,907 mutual funds then in existence. During 2007, the number of shareholders fell by 555,569 and the value of their assets, by 6.1%. Only 30 of the 935 mutual funds with a 10-year history outperformed the benchmark and only two of them outperformed the overall index of the Madrid Stock Exchange (ITBM). If in the past 16 years every mutual fund had achieved the benchmark return for its category, the gain in value would have been 180 billion euros, instead of the actual figure of 80 billion euros. Total fees and other expenses for the period amounted to 34 billion euros.mutual funds; return to shareholders; benchmark; appreciation of the funds:
Weak localization and spin splitting in inversion layers on p-type InAs
We report on the magnetoconductivity of quasi two-dimensional electron
systems in inversion layers on p-type InAs single crystals. In low magnetic
fields pronounced features of weak localization and antilocalization are
observed. They are almost perfectly described by the theory of Iordanskii,
Lyanda-Geller and Pikus. This allows us to determine the spin splitting and the
Rashba parameter of the ground electric subband as a function of the electron
density.Comment: Accepted for publication in Phys. Rev. B, 4 page
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Combining Nearest Neighbor Predictions and Model-Based Predictions of Realized Variance: Does it Pay?
The increasing availability of intraday financial data has led to improvements in daily volatility forecasting through long-memory models of realized volatility. This paper demonstrates the merit of the non-parametric Nearest Neighbor (NN) approach for S&P 100 realized variance forecasting. A priori the NN approach is appealing because it can reproduce complex dynamic dependencies while largely avoiding misspecification and parameter estimation uncertainty, unlike model-based methods. We evaluate the forecasts through straddle trading profitability metrics and using conventional statistical accuracy criteria. The ranking of individual forecasts confirms that statistical accuracy does not have a one-to-one mapping into profitability. In turbulent markets, the NN forecasts lead to higher risk-adjusted profitability even though the model-based forecasts are statistically superior. In both calm and turbulent market conditions, the directional combination of NN and model-based forecasts is more profitable than any of the individual forecasts
Special symplectic Lie groups and hypersymplectic Lie groups
A special symplectic Lie group is a triple such that
is a finite-dimensional real Lie group and is a left invariant
symplectic form on which is parallel with respect to a left invariant
affine structure . In this paper starting from a special symplectic Lie
group we show how to ``deform" the standard Lie group structure on the
(co)tangent bundle through the left invariant affine structure such
that the resulting Lie group admits families of left invariant hypersymplectic
structures and thus becomes a hypersymplectic Lie group. We consider the affine
cotangent extension problem and then introduce notions of post-affine structure
and post-left-symmetric algebra which is the underlying algebraic structure of
a special symplectic Lie algebra. Furthermore, we give a kind of double
extensions of special symplectic Lie groups in terms of post-left-symmetric
algebras.Comment: 32 page
On paraquaternionic submersions between paraquaternionic K\"ahler manifolds
In this paper we deal with some properties of a class of semi-Riemannian
submersions between manifolds endowed with paraquaternionic structures, proving
a result of non-existence of paraquaternionic submersions between
paraquaternionic K\"ahler non locally hyper paraK\"ahler manifolds. Then we
examine, as an example, the canonical projection of the tangent bundle, endowed
with the Sasaki metric, of an almost paraquaternionic Hermitian manifold.Comment: 13 pages, no figure
Thermal performance analysis of the double sided-linear switched reluctance motor
This paper presents an exhaustive study about the propulsion force and the thermal performance of the double-sided flat Linear Switched Reluctance Motor (LSRM) according to the number of phases (m) and the pole stroke (PS). The analysis is performed by means of the Finite Element Method (FEM) for electromagnetic computations and a lumped parameter for thermal model (LPT) both linked to an optimization algorithm based on the Response Surface Methodology (RSM) in order to reduce the computing time. The results show the optimal design of LSRM from the point of view of the thermo-mechanical performance for a given insulation class and a duty cycle operating conditions
Visuomotor learning promotes visually evoked activity in the medial prefrontal cortex
The medial prefrontal cortex (mPFC) is necessary for executing many learned associations between stimuli and movement. It is unclear, however, how activity in the mPFC evolves across learning, and how this activity correlates with sensory stimuli and the learned movements they evoke. To address these questions, we record cortical activity with widefield calcium imaging while mice learned to associate a visual stimulus with a forelimb movement. After learning, the mPFC shows stimulus-evoked activity both during task performance and during passive viewing, when the stimulus evokes no action. This stimulus-evoked activity closely tracks behavioral performance across training, with both exhibiting a marked increase between days when mice first learn the task, followed by a steady increase with further training. Electrophysiological recordings localized this activity to the secondary motor and anterior cingulate cortex. We conclude that learning a visuomotor task promotes a route for visual information to reach the prefrontal cortex
Shot noise and spin-orbit coherent control of entangled and spin polarized electrons
We extend our previous work on shot noise for entangled and spin polarized
electrons in a beam-splitter geometry with spin-orbit (\textit{s-o})
interaction in one of the incoming leads (lead 1). Besides accounting for both
the Dresselhaus and the Rashba spin-orbit terms, we present general formulas
for the shot noise of singlet and triplets states derived within the scattering
approach. We determine the full scattering matrix of the system for the case of
leads with \textit{two} orbital channels coupled via weak \textit{s-o}
interactions inducing channel anticrossings. We show that this interband
coupling coherently transfers electrons between the channels and gives rise to
an additional modulation angle -- dependent on both the Rashba and Dresselhaus
interaction strengths -- which allows for further independent coherent control
of the electrons traversing the incoming leads. We derive explicit shot noise
formulas for a variety of correlated pairs (e.g., Bell states) and lead spin
polarizations. Interestingly, the singlet and \textit{each} of the triplets
defined along the quantization axis perpendicular to lead 1 (with the local
\textit{s-o} interaction) and in the plane of the beam splitter display
distinctive shot noise for injection energies near the channel anticrossings;
hence, one can tell apart all the triplets, in addition to the singlet, through
noise measurements. We also find that spin-orbit induced backscattering within
lead 1 reduces the visibility of the noise oscillations, due to the additional
partition noise in this lead. Finally, we consider injection of two-particle
wavepackets into leads with multiple discrete states and find that two-particle
entanglement can still be observed via noise bunching and antibunching.Comment: 30 two-column pages and 7 figure
Expectations and Preferences for Counseling and Psychotherapy in Native Americans
We provide a broad overview of the research on expectations and preferences for counseling and psychotherapy with Native Americans and identify a critical lack of research in this area. We conclude that increased research could improve the effectiveness of counseling and psychotherapy for Native peoples. For example, understanding and engaging patients’ expectations and preferences would likely lead to increased retention and satisfaction. Finally, we suggest that a Native American clinical practice network might be one way to generate clinical and research knowledge in the area of expectations and preferences for psychotherapy and counseling
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