1,814 research outputs found

    Admissible strategies in semimartingale portfolio selection

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    The choice of admissible trading strategies in mathematical modelling of financial markets is a delicate issue, going back to Harrison and Kreps [HK79]. In the context of optimal portfolio selection with expected utility preferences this question has been the focus of considerable attention over the last twenty years. We propose a novel notion of admissibility that has many pleasant features { admissibility is characterized purely under the objective measure P; each admissible strategy can be approximated by simple strategies using finite number of trading dates; the wealth of any admissible strategy is a supermartingale under all pricing measures; local boundedness of the price process is not required; neither strict monotonicity, strict concavity nor differentiability of the utility function are necessary; the definition encompasses both the classical mean-variance preferences and the monotone expected utility. For utility functions finite on R, our class represents a minimal set containing simple strategies which also contains the optimizer, under conditions that are milder than the celebrated reasonable asymptotic elasticity condition on the utility function

    A proposal for the idea of a flexible-combination polypill in arterial hypertension

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    Objective: Modern pharmaceutical strategies in arterial hypertension, as well as in other fields, are directed toward two major apparently contrasting objectives: 1) sim- plification of treatment by grouping multiple drugs into single fixed-combination pharmaceutical units (including “polypill”) to improve patient adherence, and 2: personalization of therapy to tailor treatments according to specific individual aspects including pharmacogenomics. The combined fulfillment of these objectives would conceivably entail the unre- alistic development of a very great variety of fixed-combination polypills, each different for drug composition and dosage. An alternative view that could combine the need for both therapy simplification and personalization may be the concept of a flexible-combination polypill. Design and Methods: In order to test this approach, we are devising a preliminary study aimed to assess the feasibility and efficacy of shifting individual patients’ treatment from multiple daily administration (multi-administration) to a single once-a-day administration (mono-administration) of the same drugs. After approval of Ethical Committee, a cross-over randomized study will be carried out for 24 weeks in 52 well controlled non complicated hypertensive outpatients under multiple therapy with at least one hypotensive drug and/or a statin and/or aspirin. Each subject will remain for an 8 weeks period on multi-administration and for another 8 weeks period on mono-administration of the same therapy; the two peri- ods will be separated by 8 weeks to avoid a carry-over effect and their sequence will be randomized

    Parameters for a Super-Flavor-Factory

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    A Super Flavor Factory, an asymmetric energy e+e- collider with a luminosity of order 10^36 cm-2s-1, can provide a sensitive probe of new physics in the flavor sector of the Standard Model. The success of the PEP-II and KEKB asymmetric colliders in producing unprecedented luminosity above 10^34 cm-2s-1 has taught us about the accelerator physics of asymmetric e+e- colliders in a new parameter regime. Furthermore, the success of the SLAC Linear Collider and the subsequent work on the International Linear Collider allow a new Super-Flavor collider to also incorporate linear collider techniques. This note describes the parameters of an asymmetric Flavor-Factory collider at a luminosity of order 10^36 cm-2s-1 at the Upsilon(4S) resonance and about 10^35 cm-2s-1 at the Tau production threshold. Such a collider would produce an integrated luminosity of about 10,000 fb-1 (10 ab-1) in a running year (10^7 sec) at the Upsilon(4S) resonance.Comment: Flavor Physics & CP Violation Conference, Vancouver, 200

    Association of a homozygous GCK missense mutation with mild diabetes

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    Background: Homozygous inactivating GCK mutations have been repeatedly reported to cause severe hyperglycemia, presenting as permanent neonatal diabetes mellitus (PNDM). Conversely, only two cases of GCK homozygous mutations causing mild hyperglycemia have been so far described. We here report a novel GCK mutation (c.1116G>C, p.E372D), in a family with one homozygous member showing mild hyperglycemia. Methods: GCK mutational screening was carried out by Sanger sequencing. Computational analyses to investigate pathogenicity and molecular dynamics (MD) were performed for GCK-E372D and for previously described homozygous mutations associated with mild (n = 2) or severe (n = 1) hyperglycemia, used as references. Results: Of four mildly hyperglycemic family-members, three were heterozygous and one, diagnosed in the adulthood, was homozygous for GCK-E372D. Two nondiabetic family members carried no mutations. Fasting glucose (p = 0.016) and HbA1c (p = 0.035) correlated with the number of mutated alleles (0–2). In-silico predicted pathogenicity was not correlated with the four mutations’ severity. At MD, GCK-E372D conferred protein structure flexibility intermediate between mild and severe GCK mutations. Conclusions: We present the third case of homozygous GCK mutations associated with mild hyperglycemia, rather than PNDM. Our in-silico analyses support previous evidences suggesting that protein stability plays a role in determining clinical severity of GCK mutations

    Unitary and analytic model of nucleon EM structure, the puzzle with JLab proton polarization data and new insight into proton charge distribution

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    The Unitary and analytic model of nucleon electromagnetic structure, describing all existing nucleon form factor data, is briefly reviewed. Then in the framework of this model the problem of inconsistency of older proton electric form factor data in space-like region (obtained from ep% e^{-}p\to e^{-}p process by the Rosenbluth technique) with recent Jefferson Lab data on the ratio GEp(t)/GMp(t)G_{Ep}(t)/G_{Mp}(t) (measured in precise polarization epep\overrightarrow{e}^{-}p\to e^{-}\overrightarrow{p} experiment) is suggested to be solved in favour of the latter data which, however, unlike older data cause an existence of the form factor zero, i.e. a difraction minimum in GEp(t)|G_{Ep}(t)| around t=Q2=13t=-Q^{2}=-13GeV2^{2}. The new behaviour of GEp(t)G_{Ep}(t) with the zero gives modified proton charge distribution with enlarged value of the mean square charge radius.Comment: 9 pages, 11 eps figures. Talk presented at the workshop on Lepton Scattering and the Structure of Hadrons and Nuclei, Erice (Italy), September 200

    Magnetic-field-induced Luttinger liquid

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    It is shown that a strong magnetic field applied to a bulk metal induces a Luttinger-liquid phase. This phase is characterized by the zero-bias anomaly in tunneling: the tunneling conductance scales as a power-law of voltage or temperature. The tunneling exponent increases with the magnetic field as BlnB. The zero-bias anomaly is most pronounced for tunneling with the field applied perpendicular to the plane of the tunneling junction.Comment: a reference added, minor typos correcte

    Nucleation of superconducting pairing states at mesoscopic scales at zero temperature

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    We find the spin polarized disordered Fermi liquids are unstable to the nucleation of superconducting pairing states at mesoscopic scales even when magnetic fields which polarize the spins are substantially higher than the critical one. We study the probability of finding superconducting pairing states at mesoscopic scales in this limit. We find that the distribution function depends only on the film conductance. The typical length scale at which pairing takes place is universal, and decreases when the magnetic field is increased. The number density of these states determines the strength of the random exchange interactions between mesoscopic pairing states.Comment: 11 pages, no figure

    2D/3D SOIL CONSUMPTION TRACKING IN A MARBLE QUARRY DISTRICT

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    Abstract. Complex extractive districts, such as the marble quarries in the Apuan Alps (northern Italy), require soil consumption monitoring over the years that could be achieved through high-resolution remotely sensed data. To derive 2D and 3D indicators with appropriate resolution for annual monitoring of high-resolution changes in soil consumption, aerial images, LiDAR acquisitions, satellite data, and Remotely Piloted Aircraft Systems (RPAS) acquisitions were used. In particular, open-access Sentinel-2 multispectral satellite imagery with a spatial resolution of 10 m was used to assess cover changes (2D), and then refined by manual interpretation for 5 years (2016-2021). 3D changes were detected by comparing free aerial LiDAR data from 2009 and 2017, integrated with two stereo models obtained from Pléiades high-resolution satellite images from 2020 and 2022. 3D changes observed over the years by algebraic elevation comparison, performed in QGIS 3.x environment, highlight quarries characterized by intense mining activities (extracted marble blocks, characterized by positive elevation differences) and quarry area management (debris disposal and service infrastructure construction, characterized by negative elevation differences). The combined use of 2D and 3D change indicators can be challenging in order to correctly represent soil consumption over the years. A dual 2D/3D webgis client have been developed for proper representation of 2D/3D spatial indicators of ongoing extraction activities in the Carrara marble basin: high-resolution images have been served as tiled data, while 2D/3D spatial indicators are served as static and/or tiled vector data. Open-Source libraries have used in data processing, serving and representation inside a map interface

    The robust Merton problem of an ambiguity averse investor

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    We derive a closed form portfolio optimization rule for an investor who is diffident about mean return and volatility estimates, and has a CRRA utility. Confidence is here represented using ellipsoidal uncertainty sets for the drift, given a (compact valued) volatility realization. This specification affords a simple and concise analysis, as the agent becomes observationally equivalent to one with constant, worst case parameters. The result is based on a max–min Hamilton–Jacobi–Bellman–Isaacs PDE, which extends the classical Merton problem and reverts to it for an ambiguity-neutral investor. © 2016, Springer-Verlag Berlin Heidelberg
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