Search results for "Replica"
showing 10 items of 576 documents
Fuzzy portfolio optimization under downside risk measures
2007
This paper presents two fuzzy portfolio selection models where the objective is to minimize the downside risk constrained by a given expected return. We assume that the rates of returns on securities are approximated as LR-fuzzy numbers of the same shape, and that the expected return and risk are evaluated by interval-valued means. We establish the relationship between those mean-interval definitions for a given fuzzy portfolio by using suitable ordering relations. Finally, we formulate the portfolio selection problem as a linear program when the returns on the assets are of trapezoidal form.
Bootstrap validation of links of a minimum spanning tree
2018
We describe two different bootstrap methods applied to the detection of a minimum spanning tree obtained from a set of multivariate variables. We show that two different bootstrap procedures provide partly distinct information that can be highly informative about the investigated complex system. Our case study, based on the investigation of daily returns of a portfolio of stocks traded in the US equity markets, shows the degree of robustness and completeness of the information extracted with popular information filtering methods such as the minimum spanning tree and the planar maximally filtered graph. The first method performs a "row bootstrap" whereas the second method performs a "pair bo…
Nowcasting COVID‐19 incidence indicators during the Italian first outbreak
2020
A novel parametric regression model is proposed to fit incidence data typically collected during epidemics. The proposal is motivated by real-time monitoring and short-term forecasting of the main epidemiological indicators within the first outbreak of COVID-19 in Italy. Accurate short-term predictions, including the potential effect of exogenous or external variables are provided. This ensures to accurately predict important characteristics of the epidemic (e.g., peak time and height), allowing for a better allocation of health resources over time. Parameter estimation is carried out in a maximum likelihood framework. All computational details required to reproduce the approach and replica…
Trapping the Enemy: Vermamoeba vermiformis Circumvents Faustovirus Mariensis Dissemination by Enclosing Viral Progeny inside Cysts
2019
Viruses depend on cells to replicate and can cause considerable damage to their hosts. However, hosts have developed a plethora of antiviral mechanisms to counterattack or prevent viral replication and to maintain homeostasis. Advantageous features are constantly being selected, affecting host-virus interactions and constituting a harsh race for supremacy in nature. Here, we describe a new antiviral mechanism unveiled by the interaction between a giant virus and its amoebal host. Faustovirus mariensis infects Vermamoeba vermiformis, a free-living amoeba, and induces cell lysis to disseminate into the environment. Once infected, the cells release a soluble factor that triggers the encystment…
Deep Convolutional Neural Networks for Fire Detection in Images
2017
Detecting fire in images using image processing and computer vision techniques has gained a lot of attention from researchers during the past few years. Indeed, with sufficient accuracy, such systems may outperform traditional fire detection equipment. One of the most promising techniques used in this area is Convolutional Neural Networks (CNNs). However, the previous research on fire detection with CNNs has only been evaluated on balanced datasets, which may give misleading information on real-world performance, where fire is a rare event. Actually, as demonstrated in this paper, it turns out that a traditional CNN performs relatively poorly when evaluated on the more realistically balance…
Comparison of the genotoxic and apoptosis-inducing properties of ganciclovir and penciclovir in Chinese hamster ovary cells transfected with the thym…
2000
We studied the genotoxic and apoptosis-inducing properties of ganciclovir (GCV) and penciclovir (PCV) using Chinese hamster ovary cells stably transfected with the thymidine kinase (tk) gene of herpes simplex virus-1 (HSV-1). Cells expressing HSVtk were 300 and 100 times more sensitive than their isogenic HSVtk- counterparts to the cytotoxic effects of GCV and PCV, respectively. Using radiolabeled drugs, GCV was found to be incorporated into the genomic DNA much more effectively than PCV. GCV was highly potent in inducing chromosomal aberrations compared with PCV, which provoked less sister chromatid exchanges and chromosomal changes using equimolar or equitoxic doses. For both agents, apop…
Enhancerless Cytomegalovirus Is Capable of Establishing a Low-Level Maintenance Infection in Severely Immunodeficient Host Tissues but Fails in Expon…
2010
ABSTRACT Major immediate-early transcriptional enhancers are genetic control elements that act, through docking with host transcription factors, as a decisive regulatory unit for efficient initiation of the productive virus cycle. Animal models are required for studying the function of enhancers paradigmatically in host organs. Here, we have sought to quantitatively assess the establishment, maintenance, and level of in vivo growth of enhancerless mutants of murine cytomegalovirus in comparison with those of an enhancer-bearing counterpart in models of the immunocompromised or immunologically immature host. Evidence is presented showing that enhancerless viruses are capable of forming restr…
Patchwork Pattern of Transcriptional Reactivation in the Lungs Indicates Sequential Checkpoints in the Transition from Murine Cytomegalovirus Latency…
1999
The lungs are a relevant organ site of primary and recurrent human cytomegalovirus (hCMV) disease (for overviews, see references 21, 22, 31, 34, 39, and 44). Murine CMV (mCMV) can serve us as a model for studying CMV pneumonia in acute infection (6, 27, 33, 37) as well as for studying viral latency, reactivation, and recurrence in the lungs (2, 17, 18, 42, 43). We have shown recently that transcription from the major immediate-early (MIE) transcription unit ie1-ie3 (hereafter referred to as ie1/3), which is driven by a strong MIE promoter-enhancer (MIEPE) (3), occurs during pulmonary latency of mCMV but fails to initiate the productive cycle (17). Notably, the paralogous MIEPE of hCMV can f…
Dealing with the Pseudo-Replication Problem in Longitudinal Data from Posidonia Oceanica Surveys: Modeling Dependence vs. Subsampling
2012
Posidonia oceanica represents the key species of the most important ecosystem in subtidal habitats of the Mediterranean Sea. Being sensitive to changes in the environment, it is considered a crucial indicator of the quality of coastal marine waters. A peculiarity of P. oceanica is the presence of reiterative modules characterizing its growth, which lend themselves to back-dating techniques, allowing for the reconstruction of past history of growth variables (annual rhizome elongation and diameter, primary production, etc.). Such back-dating techniques provide, for each sampled shoot, a longitudinal series of multivariate data; this is an instance of what Hurlbert (1984) in a seminal paper d…
Reply to Côté and Willer: New replication attempts provide no evidence that inequality moderates the effect of income on generosity
2020
Cote et al. (1) provided evidence that economic inequality moderates the effect of income on generosity. In their study, individuals with higher household income were less generous in a dictator game than poorer individuals only if they resided in a US state with comparatively large economic inequality. We questioned this finding because we did not find any evidence for the postulated moderation effect of economic inequality across three studies (ref. 2; for similar replication failures see ref. 3). However, our studies were conceptual rather than direct replications as we used different measures of generosity (charitable donations, behavior in a trust game, and volunteering) and also inclu…