Search results for "Hypothesis"
showing 10 items of 426 documents
A Problem of Optimization in a Case of Foreign Investment
2000
The aim of the paper is to solve an optimization problem in an economic system with a central bank and a set of private agents. Each agent aims to maximize her expected utility, with rational expectations and being risk averse. The agents follow a profitability-risk criterium to face the portfolio diversification problem between foreign or domestic investment. An explicit formula for the optimal amount of foreign investment as a function of the expected exchange rate and an explicit formula for the exchange rate are obtained. These formulas show the hard influence of the expected exchange rate, the variance and the risk aversion on the agents’ decisions.
FOREIGN MONOPOLIES AND TARIFF AGREEMENTS UNDER INTEGRATED MARKETS
2005
In this paper the optimal policy and the stability of a tariff agreement among the importers of a monopolized good that is sold in an integrated market are studied. To analyze the stability, the tariff agreement formation is modelled as a two-stage game. In the first stage each importer decides whether or not to sign the agreement and in the second stage the signatories and non-signatories choose their tariff whereas the monopoly chooses the quantity or the price. The findings show that the optimal policy of the importers depends on which strategic variable is selected by the monopolist but that, on the contrary, this decision has no effects on the level of cooperation that can be reached b…
Using Internet videos to learn about controversies: Evaluation and integration of multiple and multimodal documents by primary school students
2020
Abstract In many Internet videos authors appear in front of the camera to present their particular view on a topic. Given the high consumption rate of Internet videos by teenagers, we explored the pros and cons of using these videos to learn about complex topics, compared to learning from textual web pages. Specifically, we studied how 207 primary school students (grades 4–6) evaluated and integrated multiple and multimodal web pages (text or video) while learning about the pros and cons of bottled water. Results showed no major role of modality in students' source memory, as measured by citations in their responses to an integration question and their memory for sources. Nevertheless, moda…
In Silico Insights into the SARS CoV-2 Main Protease Suggest NADH Endogenous Defences in the Control of the Pandemic Coronavirus Infection
2020
COVID-19 is a pandemic health emergency faced by the entire world. The clinical treatment of the severe acute respiratory syndrome (SARS) CoV-2 is currently based on the experimental administration of HIV antiviral drugs, such as lopinavir, ritonavir, and remdesivir (a nucleotide analogue used for Ebola infection). This work proposes a repurposing process using a database containing approximately 8000 known drugs in synergy structure- and ligand-based studies by means of the molecular docking and descriptor-based protocol. The proposed in silico findings identified new potential SARS CoV-2 main protease (MPRO) inhibitors that fit in the catalytic binding site of SARS CoV-2 MPRO. Several sel…
Permutation Test (PT) and Tolerated Difference Test (TDT): Two new, robust and powerful nonparametric tests for statistical comparison of dissolution…
2013
The most popular way of comparing oral solid forms of drug formulations from different batches or manufacturers is through dissolution profile comparison. Usually, a similarity factor known as (f2) is employed; However, the level of confidence associated with this method is uncertain and its statistical power is low. In addition, f2 lacks the flexibility needed to perform in special scenarios. In this study two new statistical tests based on nonparametrical Permutation Test theory are described, the Permutation Test (PT), which is very restrictive to confer similarity, and the Tolerated Difference Test (TDT), which has flexible restrictedness to confer similarity, are described and compared…
Algebraic Curves and Riemann Surfaces in Matlab
2010
In the previous chapter, a detailed description of the algorithms for the ‘algcurves’ package in Maple was presented. As discussed there, the package is able to handle general algebraic curves with coefficients given as exact arithmetic expressions, a restriction due to the use of exact integer arithmetic. Coefficients in terms of floating point numbers, i.e., the representation of decimal numbers of finite length on a computer, can in principle be handled, but the floating point numbers have to be converted to rational numbers. This can lead to technical difficulties in practice. One also faces limitations if one wants to study families of Riemann surfaces, where the coefficients in the al…
Small genomes and the difficulty to define minimal translation and metabolic machineries
2015
The notion of minimal life has sparked the interest of scientists in different fields, ranging from the origin-of-life research to biotechnology-oriented synthetic biology. Whether the interest is focused on the emergence of protocells out of prebiotic systems or the design of a cell chassis ready to incorporate new devices and functions, proposing minimal combinations of genes for life is not a trivial task. Using comparative genomics and biochemistry of endosymbionts (i.e., intracellular mutualistic symbionts) and intracellular parasites, a decade ago we proposed the core of a minimal gene set for a simple heterotrophic cell adapted to a chemically complex environment. In this work, we di…
Old mathematical challenges: Precedents to the millennium problems
2018
The millennium problems set out by the Clay Mathematics Institute became a stimulus for mathematical research. The aim of this article is to highlight some previous challenges that were also a stimulus to finding proof for some interesting results. With this pretext, we present three moments in the history of mathematics that were important for the development of new lines of research. We briefly analyse the Tartaglia challenge, which brought about the discovery of a formula for third degree equations; Johan Bernoulli?s problem of the curve of fastest descent, which originated the calculus of variations; and the incidence of the problems posed by David Hilbert in 1900, focusing on the first…
On Mardia’s Tests of Multinormality
2004
Classical multivariate analysis is based on the assumption that the data come from a multivariate normal distribution. The tests of multinormality have therefore received very much attention. Several tests for assessing multinormality, among them Mardia’s popular multivariate skewness and kurtosis statistics, are based on standardized third and fourth moments. In Mardia’s construction of the affine invariant test statistics, the data vectors are first standardized using the sample mean vector and the sample covariance matrix. In this paper we investigate whether, in the test construction, it is advantageous to replace the regular sample mean vector and sample covariance matrix by their affi…
Locally optimal invariant detector for testing equality of two power spectral densities
2018
This work addresses the problem of determining whether two multivariate random time series have the same power spectral density (PSD), which has applications, for instance, in physical-layer security and cognitive radio. Remarkably, existing detectors for this problem do not usually provide any kind of optimality. Thus, we study here the existence under the Gaussian assumption of optimal invariant detectors for this problem, proving that the uniformly most powerful invariant test (UMPIT) does not exist. Thus, focusing on close hypotheses, we show that the locally most powerful invariant test (LMPIT) only exists for univariate time series. In the multivariate case, we prove that the LMPIT do…