751 research outputs found
A review of the Dividend Discount Model: from deterministic to stochastic models
This chapter presents a review of the dividend discount models starting from
the basic models (Williams 1938, Gordon and Shapiro 1956) to more recent and
complex models (Ghezzi and Piccardi 2003, Barbu et al. 2017, D'Amico and De
Blasis 2018) with a focus on the modelling of the dividend process rather than
the discounting factor, that is assumed constant in most of the models. The
Chapter starts with an introduction of the basic valuation model with some
general aspects to consider when performing the computation. Then, Section 1.3
presents the Gordon growth model (Gordon 1962) with some of its extensions
(Malkiel 1963, Fuller and Hsia 1984, Molodovsky et al. 1965, Brooks and Helms
1990, Barsky and De Long 1993), and reports some empirical evidence. Extended
reviews of the Gordon stock valuation model and its extensions can be found in
Kamstra (2003) and Damodaran (2012). In Section 1.4, the focus is directed to
more recent advancements which make us of the Markov chain to model the
dividend process (Hurley and Johnson 1994, Yao 1997, Hurley and Johnson 1998,
Ghezzi and Piccardi 2003, Barbu et al. 2017, D'Amico and De Blasis 2018). The
advantage of these models is the possibility to obtain a different valuation
that depends on the state of the dividend series, allowing the model to be
closer to reality. In addition, these models permit to obtain a measure of the
risk of the single stock or a portfolio of stocks
Exploring nu signals in dark matter detectors
We investigate standard and non-standard solar neutrino signals in direct
dark matter detection experiments. It is well known that even without new
physics, scattering of solar neutrinos on nuclei or electrons is an irreducible
background for direct dark matter searches, once these experiments each the ton
scale. Here, we entertain the possibility that neutrino interactions are
enhanced by new physics, such as new light force carriers (for instance a "dark
photon") or neutrino magnetic moments. We consider models with only the three
standard neutrino flavors, as well as scenarios with extra sterile neutrinos.
We find that low-energy neutrino--electron and neutrino--nucleus scattering
rates can be enhanced by several orders of magnitude, potentially enough to
explain the event excesses observed in CoGeNT and CRESST. We also investigate
temporal modulation in these neutrino signals, which can arise from geometric
effects, oscillation physics, non-standard neutrino energy loss, and
direction-dependent detection efficiencies. We emphasize that, in addition to
providing potential explanations for existing signals, models featuring new
physics in the neutrino sector can also be very relevant to future dark matter
searches, where, on the one hand, they can be probed and constrained, but on
the other hand, their signatures could also be confused with dark matter
signals.Comment: 38 pages, 8 figures, 1 table; v3: eq 3 and nuclear recoil plots
corrected, footnote added, conclusions unchange
NEST: A Comprehensive Model for Scintillation Yield in Liquid Xenon
A comprehensive model for explaining scintillation yield in liquid xenon is
introduced. We unify various definitions of work function which abound in the
literature and incorporate all available data on electron recoil scintillation
yield. This results in a better understanding of electron recoil, and
facilitates an improved description of nuclear recoil. An incident gamma energy
range of O(1 keV) to O(1 MeV) and electric fields between 0 and O(10 kV/cm) are
incorporated into this heuristic model. We show results from a Geant4
implementation, but because the model has a few free parameters, implementation
in any simulation package should be simple. We use a quasi-empirical approach,
with an objective of improving detector calibrations and performance
verification. The model will aid in the design and optimization of future
detectors. This model is also easy to extend to other noble elements. In this
paper we lay the foundation for an exhaustive simulation code which we call
NEST (Noble Element Simulation Technique).Comment: 24 pages, 9 figures, 3 table
Haldane-Gapped Spin Chains as Luttinger Liquids: Correlation Functions at Finite Field
We study the behavior of Heisenberg, antiferromagnetic, integer-spin chains
in the presence of a magnetic field exceeding the attendant spin gap. For
temperatures much smaller than the gap, the spin chains exhibit Luttinger
liquid behavior. We compute exactly both the corresponding Luttinger parameter
and the Fermi velocity as a function of magnetic field. This enables the
computation of a number of correlators from which we derive the spin
conductance, the expected form of the dynamic structure factor relevant to
inelastic neutron scattering experiments, and NMR relaxation rates. We also
comment upon the robustness of the magnetically induced gapless phase both to
finite temperature and finite couplings between neighbouring chains.Comment: 32 pages, 8 figures; published version includes additions discussing
the robustness of the magnetically induced gapless phase to ordering between
chains as well as the relationship between the spin-1 chains and spin-1/2
ladders in the presence of a magnetic fiel
Functional diversity of chemokines and chemokine receptors in response to viral infection of the central nervous system.
Encounters with neurotropic viruses result in varied outcomes ranging from encephalitis, paralytic poliomyelitis or other serious consequences to relatively benign infection. One of the principal factors that control the outcome of infection is the localized tissue response and subsequent immune response directed against the invading toxic agent. It is the role of the immune system to contain and control the spread of virus infection in the central nervous system (CNS), and paradoxically, this response may also be pathologic. Chemokines are potent proinflammatory molecules whose expression within virally infected tissues is often associated with protection and/or pathology which correlates with migration and accumulation of immune cells. Indeed, studies with a neurotropic murine coronavirus, mouse hepatitis virus (MHV), have provided important insight into the functional roles of chemokines and chemokine receptors in participating in various aspects of host defense as well as disease development within the CNS. This chapter will highlight recent discoveries that have provided insight into the diverse biologic roles of chemokines and their receptors in coordinating immune responses following viral infection of the CNS
A multi-layered view of chemical and biochemical engineering
The contents of this article are based on the results of discussions the corresponding author has had since 2015 with the co-authors, who are members of academia and industry in Europe, on the scope and significance of chemical and biochemical engineering as a discipline. The result is a multi-layered view of chemical and biochemical engineering where the inner-layer deals with the fundamental principles and their application; the middle-layer deals with consolidation and expansion of the principles through a combination of science and engineering, leading to the development of sustainable technologies; and the outer-layer deals with integration of knowledge and collaboration with other disciplines to achieve a more sustainable society. Through this multi-layered view several important issues with respect to education, research and practice are highlighted together with current and future challenges and opportunities
The injustice of unfit clinical practice guidelines in low-resource realities
To end the international crisis of preventable deaths in low-income and middle-income countries, evidence-informed and cost-efficient health care is urgently needed, and contextualised clinical practice guidelines are pivotal. However, as exposed by indirect consequences of poorly adapted COVID-19 guidelines, fundamental gaps continue to be reported between international recommendations and realistic best practice. To address this long-standing injustice of leaving health providers without useful guidance, we draw on examples from maternal health and the COVID-19 pandemic. We propose a framework for how global guideline developers can more effectively stratify recommendations for low-resource settings and account for predictable contextual barriers of implementation (eg, human resources) as well as gains and losses (eg, cost-efficiency). Such development of more realistic clinical practice guidelines at the global level will pave the way for simpler and achievable adaptation at local levels. We also urge the development and adaptation of high-quality clinical practice guidelines at national and subnational levels in low-income and middle income countries through co-creation with end-users, and we encourage global sharing of these experiences.Research into fetal development and medicin
Trends in autoionization of Rydberg states converging to the 4s threshold in the Kr-Rbâș-SrÂČâș isoelectonic sequence: theory and experiment
We have measured the photoabsorption spectra of the Kr-like ions Rb+ and Sr2+ at photon energies corresponding to the excitation of 4s-np resonances using, the dual laser plasma photoabsorption technique. Dramatic changes in the line profiles, with increasing ionization and also proceeding along the Rydberg series of each ion, are observed and explained by the trends in 4s-transition amplitudes computed within a framework of configuration-interaction Pauli-Fock calculations. Total photoionization cross sections show very good agreement with relative absorption data extracted from the measured spectra
Single Spin Asymmetry in Polarized Proton-Proton Elastic Scattering at GeV
We report a high precision measurement of the transverse single spin
asymmetry at the center of mass energy GeV in elastic
proton-proton scattering by the STAR experiment at RHIC. The was measured
in the four-momentum transfer squared range \GeVcSq, the region of a significant interference between the
electromagnetic and hadronic scattering amplitudes. The measured values of
and its -dependence are consistent with a vanishing hadronic spin-flip
amplitude, thus providing strong constraints on the ratio of the single
spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated
by the Pomeron amplitude at this , we conclude that this measurement
addresses the question about the presence of a hadronic spin flip due to the
Pomeron exchange in polarized proton-proton elastic scattering.Comment: 12 pages, 6 figure
- âŠ