High-dimensional and one-class classification

When dealing with high-dimensional data and, in particular, when the number of attributes p is large comparatively to the sample size n, several classification methods cannot be applied. Fisher's linear discriminant rule or the quadratic discriminant one are unfeasible, as the inverse of the involved covariance matrices cannot be computed. A recent approach to overcome this problem is based on Random Projections (RPs), which have emerged as a powerful method for dimensionality reduction. In 2017, Cannings and Samworth introduced the RP method in the ensemble context to extend to the high-dimensional domain classification methods originally designed for low-dimensional data. Although the RP ensemble classifier allows improving classification accuracy, it may still include redundant information. Moreover, differently from other ensemble classifiers (e.g. Random Forest), it does not provide any insight on the actual classification importance of the input features. To account for these aspects, in the first part of this thesis, we investigate two new directions of the RP ensemble classifier. Firstly, combining the original idea of using the Multiplicative Binomial distribution as the reference model to describe and predict the ensemble accuracy and an important result on such distribution, we introduce a stepwise strategy for post-pruning (called Ensemble Selection Algorithm). Secondly, we propose a criterion (called Variable Importance in Projection) that uses the feature coefficients in the best discriminant projections to measure the variable importance in classification. In the second part, we faced the new challenges posed by the high-dimensional data in a recently emerging classification context: one-class classification. This is a special classification task, where only one class is fully known (the target class), while the information on the others is completely missing. In particular, we address this task by using Gini's transvariation probability as a measure of typicality, aimed at identifying the best boundary around the target class

Piezoelectric effect and electroactive phase nucleation in self-standing films of unpoled PVDF nanocomposite films

Novel polymer-based piezoelectric nanocomposites with enhanced electromechanical properties open new opportunities for the development of wearable energy harvesters and sensors. This paper investigates how the dissolution of different types of hexahydrate metal salts affects β-phase content and piezoelectric response (d33) at nano-and macroscales of polyvinylidene fluoride (PVDF) nanocomposite films. The strongest enhancement of the piezoresponse is observed in PVDF nanocomposites processed with Mg(NO3)2·6H2O. The increased piezoresponse is attributed to the synergistic effect of the dipole moment associated with the nucleation of the electroactive phase and with the electrostatic interaction between the CF2group of PVDF and the dissolved salt through hydrogen bonding. The combination of nanofillers like graphene nanoplatelets or zinc oxide nanorods with the hexahydrate salt dissolution in PVDF results in a dramatic reduction of d33, because the nanofiller assumes a competitive role with respect to H-bond formation between PVDF and the dissolved metal salt. The measured peak value of d33reaches the local value of 13.49 pm/V, with an average of 8.88 pm/V over an area of 1 cm2. The proposed selection of metal salt enables low-cost production of piezoelectric PVDF nanocomposite films, without electrical poling or mechanical stretching, offering new opportunities for the development of devices for energy harvesting and wearable sensors

Post-marketing surveillance study of the DTaP2-IPV-HB-Hib (Hexyon) vaccine administered in preterm infants in the Apulia region, Italy, in 2017.

Recommendations in many countries state that preterm infants (PTIs) should receive the same routine immunization schedule and timing as for full-term births, according to their chronological age. Data regarding hexavalent vaccine safety in PTIs are still limited. We conducted a post-marketing surveillance study of the DTaP2-IPV-HB-Hib vaccine administered to PTIs in Apulia region, Italy. We identified PTIs by selecting the hospital discharge records of infants born between January and June 2017 using the DRG and ICD-9-CM codes for preterm birth, and we matched these data with records included in the regional immunization registry. We analyzed coverage and timeliness of vaccination. To investigate adverse events (AEs) after the first dose, we interviewed via phone the parents of PTIs vaccinated with at least one dose of the DTaP2-IPV-HB-Hib vaccine. At the time of our analysis (31.12.2017), 866/936 (92.5%) PTIs received the first dose of hexavalent vaccine and 539/936 (57.6%) were vaccinated by the third month of age, as recommended; 700/866 (80.8%) received the DTaP2-IPV-HB-Hib vaccine. The parents of 339 PTIs vaccinated with the DTaP2-IPV-HB-Hib vaccine reported local pain as the most common reaction (35.7% of the children). Erythema, swelling, induration and nodule were also reported in about 25% of the children. Systemic adverse events were generally rarer than local reactions. No serious AEs were reported. Our findings showed that more than 40% of PTIs received delayed hexavalent vaccination. This study showed a reassuring safety profile of the vaccine in the preterm population and may be considered as a pilot for further real-world studies

The association between overweight and illegal drug consumption in adolescents is there an underlying influence of the sociocultural environment?

Background: The aims of the study were to: a) Examine the distribution of gender-stratified body mass index (BMI), eating attitudes and use of addictive substances, under the hypothesis of a confluent prevalence of weight abnormalities, eating disorders and substance abuse. b) Demonstrate the extent to which family, peer-related and psychosocial factors are common elements in categories of compulsive behaviour. Methodology/Principal Findings: In the present cross-sectional study, data were collected through self reported questionnaires administered to a large sample of 33,185 15-19 years old adolescents (ESPADHItalia), divided into weight categories based on the BMI percentile distribution. Multinomial analyses were adopted to address the influence of social, family, leisure time factors, Eating Attitude Test (EAT26) on the association between weight categories and drug use. Recent drugs use was more frequent in overweight and underweight adolescents (p,0.05), especially in females. An EAT26 score $20 was more common in overweight adolescents. Multinomial analysis abolished the relationship between overweight and the use of most drugs, implicating self-esteem, parents\u27 educational level, and friendships as mediators of the association. Within the overweight category, adolescents reporting recent drug use, showed greater frequency of having drug-abusing friends (,80%), and severe problems with parents and school (,30%) compared to overweight adolescents without recent drug use. Conclusion: The frequent association of overweight and substance use and the presence of common underlying social factors, highlights the need for an interdisciplinary approach involving individual-focused treatment models as well as public health, social and environmental changes to reduce food- and substances-related problems.

Rapid Spread of the SARS-CoV-2 Variant of Concern 202012/01 in Southern Italy (December 2020–March 2021)

Epidemiological and virological studies have revealed that SARS-CoV-2 variants of concern (VOCs) are emerging globally, including in Europe. The aim of this study was to evaluate the spread of B.1.1.7-lineage SARS-CoV-2 in southern Italy from December 2020–March 2021 through the detection of the S gene target failure (SGTF), which could be considered a robust proxy of VOC B.1.1.7. SGTF was assessed on 3075 samples from week 52/2020 to week 10/2021. A subset of positive samples identified in the Apulia region during the study period was subjected to whole-genome sequencing (WGS). A descriptive and statistical analysis of the demographic and clinical characteristics of cases according to SGTF status was performed. Overall, 20.2% of samples showed SGTF; 155 strains were confirmed as VOC 202012/01 by WGS. The proportion of SGTF-positive samples rapidly increased over time, reaching 69.2% in week 10/2021. SGTF-positive cases were more likely to be symptomatic and to result in hospitalization (p < 0.0001). Despite the implementation of large-scale non-pharmaceutical interventions (NPIs), such as the closure of schools and local lockdowns, a rapid spread of VOC 202012/01 was observed in southern Italy. Strengthened NPIs and rapid vaccine deployment, first among priority groups and then among the general population, are crucial both to contain the spread of VOC 202012/01 and to flatten the curve of the third wav

REDUCTION OF INVASIVE DISEASE IN CHILDREN TWO DECADES AFTER THE INTRODUCTION OF HAEMOPHILUS INFLUENZAE TYPE B CONJUGATE VACCINATION IN APULIA REGION, ITALY

Background Haemophilus influenzae type b conjugate (Hib) monovalent vaccination, consisting of 2p+1 doses at 3, 5, and 11 months of age, was introduced in the Italy’s infant immunization schedule in 1999 and included in the DTaP-HBV-IPV/Hib hexavalent vaccine since 2001. The estimated vaccination coverage was 83.4% in 2002, >90% by 2005, and >95% by 2011 [1-4]. In the Apulia region of Italy (about 4,000,000 inhabitants), vaccination coverage for 3 doses reached 75% in 2001, >90% by 2002, and >95% by 2007 (Graph. 1).Methods We considered annual age-specific hospitalization rates in infants <1 year and children 1-4 years as a proxy for incidence in the period 1996-2014. The attributable benefit was calculated as the reduction in incidence of Haemophilus influenzae invasive disease among vaccinated children attributable to the routine use of Hib monovalent vaccine during 1999-2000 (“Hib-monovalent period”) and of the hexavalent DTPa-HBV-IPV/Hib vaccine in the period 2001-2014 (“DTPa-HBV-IPV/Hib period”). The prevented fraction was calculated as the proportion of hypothetical total cases that were prevented by the use of monovalent and hexavalent vaccine, respectively (Panel A) [5]Results The hospitalization rate for Haemophilus influenzae invasive disease among infants decreased from 11.5 (95% CI= 1.4-21.6) per 100,000 in the 1996-1998 pre-vaccination period to 6 (95% CI= -1.4-13.3) per 100,000 in the “Hib-monovalent period”, with an estimated AleB of -5.5 per 100,000 and a PedF of 48.2%. It declined further to 1 (95% CI= -2.2-4.1) per 100,000 in the “DTaP-HBV-IPV/Hib period”, with an AleB of -10.5 per 100,000 and a PedF of 91.6% (Graph. 2). The rate of hospitalization among children aged 1-4 year remained stable at 2.4 per 100.000 from the pre- vaccination period through “Hib-monovalent period” (AleB=0; PedF=2%) and declined to 0.1 (95% CI= - 0.4-0.7) per 100,000 in the “DTaP-HBV-IPV/Hib period”, with an AleB of -2.3 per 100,000 and a PedF of 94.3% (Graph. 3)Conclusions * Hib-monovalent period - ** DTPa-HBV-IPV/Hib period In the Apulia region of Italy, the proportion of Haemophilus influenzae invasive disease requiring hospitalization in children aged <5 years presumably prevented by the introduction of Hib universal vaccination amounted to more than nine in ten cases. These findings are consistent with increased vaccine coverage rates as a result of the wide use of the hexavalent combination vaccines