Sparse and stable Markowitz portfolios

We consider the problem of portfolio selection within the classical Markowitz mean-variance framework, reformulated as a constrained least-squares regression problem. We propose to add to the objective function a penalty proportional to the sum of the absolute values of the portfolio weights. This penalty regularizes (stabilizes) the optimization problem, encourages sparse portfolios (i.e. portfolios with only few active positions), and allows to account for transaction costs. Our approach recovers as special cases the no-short-positions portfolios, but does allow for short positions in limited number. We implement this methodology on two benchmark data sets constructed by Fama and French. Using only a modest amount of training data, we construct portfolios whose out-of-sample performance, as measured by Sharpe ratio, is consistently and significantly better than that of the naive evenly-weighted portfolio which constitutes, as shown in recent literature, a very tough benchmark.Comment: Better emphasis of main result, new abstract, new examples and figures. New appendix with full details of algorithm. 17 pages, 6 figure

Virtualized eNB Latency Limits

In flexible functional split, functions of a virtualized evolved NodeB (eNB) can be disaggregated in distributed computational resources. One of the main constraints for their placement is the latency experienced by the communication between the Virtual Machines (VM) hosting the functions. This paper evaluates experimentally the latency limits for different functional splits providing insights on flexible functional split implementationThis work has been partially funded by the EU H2020 5G-Transformer Project (grant no. 761536

Common faith or parting ways? A time varying parameters factor analysis of euro-area inflation

We analyze the interaction among the common and country specific components for the inflation rates in twelve euro area countries through a factor model with time varying parameters. The variation of the model parameters is driven by the score of the predictive likelihood, so that, conditionally on past data, the model is Gaussian and the likelihood function can be evaluated using the Kalman filter. The empirical analysis uncovers significant variation over time in the model parameters. We find that, over an extended time period, inflation persistence has fallen over time and the importance of common shocks has increased relatively to the idiosyncratic disturbances. According to the model, the fall in inflation observed since the sovereign debt crisis, is broadly a common phenomenon, since no significant cross country inflation differentials have emerged. Stressed countries, however, have been hit by unusually large shocks

TTF-1/p63-positive poorly differentiated NSCLC: A histogenetic hypothesis from the basal reserve cell of the terminal respiratory unit

TTF-1 is expressed in the alveolar epithelium and in the basal cells of distal terminal bronchioles. It is considered the most sensitive and specific marker to define the adenocarcinoma arising from the terminal respiratory unit (TRU). TTF-1, CK7, CK5/6, p63 and p40 are useful for typifying the majority of non-small-cell lung cancers, with TTF and CK7 being typically expressed in adenocarcinomas and the latter three being expressed in squamous cell carcinoma. As tumors with coexpression of both TTF-1 and p63 in the same cells are rare, we describe different cases that coexpress them, suggesting a histogenetic hypothesis of their origin. We report 10 cases of poorly differentiated non-small-cell lung carcinoma (PD-NSCLC). Immunohistochemistry was performed by using TTF-1, p63, p40 (∆Np63), CK5/6 and CK7. EGFR and BRAF gene mutational analysis was performed by using real-time PCR. All the cases showed coexpression of p63 and TTF-1. Six of them showing CK7+ and CK5/6− immunostaining were diagnosed as “TTF-1+ p63+ adenocarcinoma”. The other cases of PD-NSCLC, despite the positivity for CK5/6, were diagnosed as “adenocarcinoma, solid variant”, in keeping with the presence of TTF-1 expression and p40 negativity. A “wild type” genotype of EGFR was evidenced in all cases. TTF1 stained positively the alveolar epithelium and the basal reserve cells of TRU, with the latter also being positive for p63. The coexpression of p63 and TTF-1 could suggest the origin from the basal reserve cells of TRU and represent the capability to differentiate towards different histogenetic lines. More aggressive clinical and morphological features could characterize these “basal-type tumors” like those in the better known “basal-like” cancer of the breast

Control of near-infrared supercontinuum bandwidth by adjusting pump pulse duration

We experimentally and numerically investigated the impact of input pump pulse duration on the near-infrared bandwidth of supercontinuum generation in a photonic crystal fiber. We continuously stretched the temporal duration of the input pump laser (centered at 1030 nm) pulses from 500 fs up to 10 ps, while keeping fixed the pump peak power. We observed that the long-wavelength edge of the supercontinuum spectrum is increased by 200 nm as the pump pulse duration grows from 500 fs to 10 ps. We provide a quantitative fit of the experimental results by means of numerical simulations. Moreover, we have explained the observed spectral broadening enhancement induced by pump pulse energy by developing an approximate yet fully analytical model for soliton energy exchange through a series of collisions in the presence of stimulated Raman scattering

Impact of RAN Virtualization on Fronthaul Latency Budget: An Experimental Evaluation

In 3GPP the architecture of a New Radio Access Network (New RAN) has been defined where the evolved NodeB (eNB) functions can be split between a Distributed Unit (DU) and Central Unit (CU). Furthermore, in the virtual RAN (VRAN) approach, such functions can be virtualized (e.g., in simple terms, deployed in virtual machines). Based on the split type, different performance in terms of capacity and latency are requested to the network (i.e., fronthaul) connecting DU and CU. This study experimentally evaluates, in the 5G segment of the Advanced Research on NetwOrking (ARNO) testbed (ARNO-5G), the fronthaul latency requirements specified by Standard Developing Organizations (SDO) (3GPP in this specific case). Moreover it evaluates how much virtualization impacts the fronthaul latency budget for the the Option 7-1 functional split. The obtained results show that, in the considered Option 7-1 functional split, the fronthaul latency requirements are about 250 μs but they depend on the radio channel bandwidth and the number of the connected UEs. Finally virtualization further decreases the latency budget.This work has been partially funded by the EU H2020 5GTransformer Project (grant no. 761536

Immunohistochemical/histochemical double staining method in the study of columnar metaplasia of the oesophagus

Intestinal metaplasia in Barrett\u2019s oesopha- gus (BO) represents an important risk factor for oesophageal adenocarcinoma. Instead, few and controversial data are reported about the progression risk of columnar-lined oesophagus without intestinal metaplasia (CLO), posing an issue about its clinical management. The aim was to evaluate if some immunophenotyp- ic changes were present in CLO independently of the presence of the goblet cells. We studied a series of oesophageal biopsies from patients with endoscopic finding of columnar metapla- sia, by performing some immunohistochemical stainings (CK7, p53, AuroraA) combined with histochemistry (Alcian-blue and Alcian/PAS), with the aim of simultaneously assess the his- tochemical features in cells that shows an aber- rant expression of such antigens. We evidenced a cytoplasmic expression of CK7 and a nuclear expression of Aurora A and p53, both in goblet cells of BO and in non-goblet cells of CLO, some of which showing mild dysplasia. These find- ings suggest that some immunophenotypic changes are present in CLO and they can pre- cede the appearance of the goblet cells or can be present independently of them, confirming the conception of BO as the condition charac- terized by any extention of columnar epitheli- um. This is the first study in which a combined immunohistochemical/histochemical method has been applied to Barrett pathology