7,406 research outputs found
Levered and unlevered Beta
No full textWe prove that in a world without leverage cost the relationship between the levered beta ( L) and the unlevered beta ( u) is the No-costs-of-leverage formula: L = u + ( u - d) D (1 - T) / E. We also analyze 6 alternative valuation theories proposed in the literature to estimate the relationship between the levered beta and the unlevered beta (Harris and Pringle (1985), Modigliani and Miller (1963), Damodaran (1994), Myers (1974), Miles and Ezzell (1980), and practitioners) and prove that all provide inconsistent results.unleveredbeta; levered beta; asset beta; value of tax shields; required return to equity; leverage cost;
Comments on "A reconsideration of tax shield valuation" by Enrique R. Arzac and Lawrence R. Glosten
No full textWhile Arzac and Glosten (2005) affirm that "the value of tax shields depends upon the nature of the equity stochastic process, which, in turn, depends upon the free cash flow process," I prove that the value of tax shields depends only upon the nature of the stochastic process of the net increase of debt. Arzac and Glosten (2005) formulate the constant leverage ratio assumption as Dt = L•Et. The assumption of Fernández (2004) is E{Dt}= L•E{Et}, where E{•} is the expected value operator, D the value of debt, E the equity value, and L a constant. The Arzac and Glosten (2005) assumption requires continuous debt rebalancing, while mine does not. Under both financial policies, the expected leverage ratio is constant, but the Arzac and Glosten (2005) assumption is too extreme.Value of tax shields; required return to equity; cost of capital; net increase of debt;
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Solid-state photonic interfaces using semiconductor quantum dots
No full textNew technologies based on the properties of quantum mechanics promise
to revolutionise the way information is processed by outperforming what is
possible using classical devices. Examples include massively parallel processing
using quantum computers, verifiably secure communication using quantum
cryptography, and measurement with sensitivity beyond classical limitation
with quantum metrology. Realising the full potential of these technologies
necessitates the ability to communicate quantum information over large
distances, a key requirement for future quantum networks. However, developing
practical implementations of long-distance quantum communication
is challenging as it necessitates three major ingredients: light-matter interfaces,
elementary quantum operations, and quantum memories. This thesis
describes work that has been undertaken to address these requirements using
semiconductor nanotechnology.
We have first demonstrated that single InAs quantum dots embedded inside
conventional diode structures constitute high-fidelity controllable interfaces
between optical qubits and solid-state qubits. Indeed, the polarisation
state of a photon was transferred into the spin state of an electron-hole pair
and eventually restored through radiative recombination of the electron and
the hole with a fidelity up to 95%. Moreover, spins were manipulated using
subnanosecond modulation of a vertical electric field applied to the quantum
dots. By controlling this electrical modulation, we demonstrated elementary
phase-shift and spin-flip gate operations with near-unity fidelities.
An electron-hole pair confi ned in a single quantum dot has a short radiative
lifetime limiting therefore its use as an excitonic quantum memory.
The solution we proposed was to use a quantum dot molecule to control the
spatial separation of the electron and the hole and therefore prevent their
recombination. Comprehensive studies of electric field eff ects upon the photoluminescence
of quantum dot molecules lead to a clear understanding and
a good control over their physical properties. Single photons were stored in
individual quantum dot molecules up to 1μs and read out on a subnanosecond time scale. Moreover, the circular polarisation of individual photons was
transferred into the spin state of electron-hole pairs with a fidelity above
90%, which does not degrade for storage times up to the 12.5 ns repetition
period of the experiment.
Our work on single quantum dots could be extended in the near future to
allow for two-qubits quantum operations by con fining a second electron-hole
pair to be electrically manipulated. Storage of a superposition of spin states
in a quantum dot molecule should also be possible if the spin states are made
degenerate, which is feasible using the electric fi eld dependence of the energy
splitting between the spin states discussed in this thesis. We believe that
combining both approaches will lead to the development of a controllable
multi-qubit quantum memory for polarised light, a building block for long distance
quantum communication based on semiconductor nanotechnology
Shields-Darcy pipingmodel. Verschilanalyse met Sellmeijer en D-GeoFlow.
No full textHydraulic Structures and Flood Ris
Computational identification and analysis of protein short linear motifs
No full textShort linear motifs (SLiMs) in proteins can act as targets for proteolytic cleavage, sites of post-translational modification, determinants of sub-cellular localization, and mediators of protein-protein interactions. Computational discovery of SLiMs involves assembling a group of proteins postulated to share a potential motif, masking out residues less likely to contain such a motif, down-weighting shared motifs arising through common evolutionary descent, and calculation of statistical probabilities allowing for the multiple testing of all possible motifs. Much of the challenge for motif discovery lies in the assembly and masking of datasets of proteins likely to share motifs, since the motifs are typically short (between 3 and 10 amino acids in length), so that potential signals can be easily swamped by the noise of stochastically recurring motifs. Focusing on disordered regions of proteins, where SLiMs are predominantly found, and masking out non-conserved residues can reduce the level of noise but more work is required to improve the quality of high-throughput experimental datasets (e.g. of physical protein interactions) as input for computational discovery
GASP: gapped ancestral sequence prediction for proteins
No full textBackground: the prediction of ancestral protein sequences from multiple sequence alignments is useful for many bioinformatics analyses. Predicting ancestral sequences is not a simple procedure and relies on accurate alignments and phylogenies. Several algorithms exist based on Maximum Parsimony or Maximum Likelihood methods but many current implementations are unable to process residues with gaps, which may represent insertion/deletion (indel) events or sequence fragments.Results: here we present a new algorithm, GASP (Gapped Ancestral Sequence Prediction), for predicting ancestral sequences from phylogenetic trees and the corresponding multiple sequence alignments. Alignments may be of any size and contain gaps. GASP first assigns the positions of gaps in the phylogeny before using a likelihood-based approach centred on amino acid substitution matrices to assign ancestral amino acids. Important outgroup information is used by first working down from the tips of the tree to the root, using descendant data only to assign probabilities, and then working back up from the root to the tips using descendant and outgroup data to make predictions. GASP was tested on a number of simulated datasets based on real phylogenies. Prediction accuracy for ungapped data was similar to three alternative algorithms tested, with GASP performing better in some cases and worse in others. Adding simple insertions and deletions to the simulated data did not have a detrimental effect on GASP accuracy.Conclusions: GASP (Gapped Ancestral Sequence Prediction) will predict ancestral sequences from multiple protein alignments of any size. Although not as accurate in all cases as some of the more sophisticated maximum likelihood approaches, it can process a wide range of input phylogenies and will predict ancestral sequences for gapped and ungapped residues alik
The SLiMDisc server: short, linear motif discovery in proteins
No full textShort, linear motifs (SLiMs) play a critical role in many biological processes, particularly in protein-protein interactions. Overrepresentation of convergent occurrences of motifs in proteins with a common attribute (such as similar subcellular location or a shared interaction partner) provides a feasible means to discover novel occurrences computationally. The SLiMDisc (Short, Linear Motif Discovery) web server corrects for common ancestry in describing shared motifs, concentrating on the convergently evolved motifs. The server returns a listing of the most interesting motifs found within unmasked regions, ranked according to an information content-based scoring scheme. It allows interactive input masking, according to various criteria. Scoring allows for evolutionary relationships in the data sets through treatment of BLAST local alignments. Alongside this ranked list, visualizations of the results improve understanding of the context of suggested motifs, helping to identify true motifs of interest. These visualizations include alignments of motif occurrences, alignments of motifs and their homologues and a visual schematic of the top-ranked motifs. Additional options for filtering and/or re-ranking motifs further permit the user to focus on motifs with desired attributes. Returned motifs can also be compared with known SLiMs from the literature. SLiMDisc is available at: http://bioware.ucd.ie/ approximately slimdisc/
CFD simulation of moving spray shields
No full textMost wind tunnel experiments pertaining to shielded spraying have been conducted under stationary conditions. In field experiments, the interest has always focused on the investigation of drift amount. No information about the effect of a moving shield is available, not to mention the effect of travel speed and travel direction on drift reduction. In this study, by using the FLUENT computational fluid dynamics software pack-age, a double foil shield was used to investigate the effect of a moving shield on drift reduction under different travel speeds and travel directions (upwind and downwind). Related information on conventional spraying without shields was included. In addition, the moving effect of mechanical and pneumatic shields in a three-dimensional flow with only one droplet release nozzle was further compared. Results of this study indicated that local relative velocity plays an important role in controlling the drift potential of a moving sprayer: the higher the local relative velocity the greater the drift potential. When the sprayer moves upwind, drift potential increases slightly with increased travel speed. However when the sprayer moves downwind, drift potential decreases inversely with increased travel speed, as long as travel speed is less than wind velocity. For the double foil shield, moving upwind produced less drift potential than moving downwind. Simulation results of comparing three-dimensional shields showed that the double foil shield provided a drift reduction of 60.6% and 29.3% over conventional spraying when traveling upwind and downwind, respectively, at a speed of 1.34 m s(-1). The moving pneumatic shield with the best operating setting provided excellent control of drift reduction for both upwind and downwind traveling at a speed of 1.34 m s(-1)
Rarity of somatic and germline mutations of the cyclin-dependent kinase 4 inhibitor gene, CDK4I, in melanoma
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