Two Algorithms for Orthogonal Nonnegative Matrix Factorization with Application to Clustering

Approximate matrix factorization techniques with both nonnegativity and orthogonality constraints, referred to as orthogonal nonnegative matrix factorization (ONMF), have been recently introduced and shown to work remarkably well for clustering tasks such as document classification. In this paper, we introduce two new methods to solve ONMF. First, we show athematical equivalence between ONMF and a weighted variant of spherical k-means, from which we derive our first method, a simple EM-like algorithm. This also allows us to determine when ONMF should be preferred to k-means and spherical k-means. Our second method is based on an augmented Lagrangian approach. Standard ONMF algorithms typically enforce nonnegativity for their iterates while trying to achieve orthogonality at the limit (e.g., using a proper penalization term or a suitably chosen search direction). Our method works the opposite way: orthogonality is strictly imposed at each step while nonnegativity is asymptotically obtained, using a quadratic penalty. Finally, we show that the two proposed approaches compare favorably with standard ONMF algorithms on synthetic, text and image data sets.Comment: 17 pages, 8 figures. New numerical experiments (document and synthetic data sets

Dopaminergic system is differently altered in hippocampus and facial nucleus of trimethyltin rat model

Trimethyltin (TMT) is an organotin compound which is considered a useful tool to obtain an animal model of neurodegeneration associated with cognitive impairment (Pompili et al., 2011; Geloso et al., 2011). In the present work, this model was used in order to investigate the animal behaviour in association with the immunohistochemical expression of dopaminergic system (D1- and D2-like receptors and dopamine transporters DAT, VMAT-1 and -2) and cells viability (NEU-N) in the rat hippocampus and facial nucleus regions. TMT-treated group showed impaired spatial reference memory in a Morris water maze task compared to control group whereas the memory consolidation tested 24h after was preserved. In the open field, TMT-treated rats showed a decreased in time spent in rearing episodes reflecting a lower interest to explore a novel environment. In the hippocampal area of TMT-treated group, cell viability was significantly reduced by 45.9% whereas the D1, D2, DAT and VMAT- 2 receptor proteins immunoreactivity was significantly decreased by 57.5, 72.8, 64.1, 72.1%. In the facial nucleus, immunoreactivity reduction was observed only for dopamine transporters (average: 60% about) while the NEU-N reduction was 40%. These data were confirmed by real time RT-PCR analysis. These results suggest a differential involvement of the D1-type and D2-type receptors in the regulation of learning and memory. Besides, alterations on the functional ratio of DAT to VMAT-2 could predispose the cells to injury even at very low doses of TMT. The data obtained in facial nucleus demonstrate a different sensibility to xenobiotic of dopamine receptors and transporters. The TMT model could contribute to elucidate the role of dopaminergic system on two different CNS regions. Supported by PRIN 2008 - prot. 20089MANHH_002 and prot. 20089MANHH_003

RIFLESSIONI SULL’ESECUZIONE DELLA MISURA DI SICUREZZA IN REMS

Laws 81/2014 and 9/2012 regulate the progressive overcoming of the Judicial Psychiatric Hospitals (O.P.G.) and the consequent openingof the Residences for the Execution of Security Measures (R.E.M.S), thus advancing an inevitable reform to limit the duration of the securitymeasure within the maximum legal limit, and to put before the requirement and the claim of treatment before to the custodialconcept. However, these two fundamental conditions have concealed what should have been a thorough psychiatric-forensic analysis forthe identification of an organizational model based on clinical evidence. An accurate critical analysis of the current normative frameworkmust face the problem of the structural model of the REMS for the management of the different degrees of violence that an infirmsubject can carry out, the problem of the insufficiency of beds and the variability in the application of measure safety.Therefore, the purpose of this work is to discuss some problems that we consider should be examined by the scientific community, underliningalso the necessity of a new dialectical institutional phase to propose a different clinic-forensic model based on the scientific evidenceobtained in this first period of evaluation.Con le Leggi 81/2014 e 9/2012 si è assistito al progressivo superamento degli Ospedali Psichiatrici Giudiziari (O.P.G.) e alla conseguenteapertura delle Residenze per l’Esecuzione delle Misure di Sicurezza (R.E.M.S), dando così inizio ad un’inevitabile riforma per limitarela durata della misura di sicurezza entro il limite massimo di legge e per anteporre al concetto custodialista la necessità e il diritto alle cure.Queste due condizioni fondamentali, hanno però offuscato quella che sarebbe dovuta essere una più approfondita analisi psichiatricoforenseper l’individuazione di un modello organizzativo basato su evidenze cliniche. Un’accurata analisi critica sull’attuale impianto normativodeve affrontare il problema del modello strutturale delle REMS per la gestione dei diversi gradi di violenza che un soggettoinfermo può esprimere, il problema della scarsità di posti letto, e la variabilità nell’applicazione della misura di sicurezza.Lo scopo di questo lavoro è pertanto quello di affrontare alcune problematiche che riteniamo debbano essere prese in esame dalla comunitàscientifica, sottolineando anche l’esigenza di una nuova fase dialettica-istituzionale per proporre un nuovo modello clinico-forense chetenga conto delle evidenze scientifiche raccolte in questi primi anni di osservazione

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Measurement of t(t)over-bar normalised multi-differential cross sections in pp collisions at root s=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

Peer reviewe

Measurement of the top quark forward-backward production asymmetry and the anomalous chromoelectric and chromomagnetic moments in pp collisions at √s = 13 TeV

Abstract The parton-level top quark (t) forward-backward asymmetry and the anomalous chromoelectric (d̂ t) and chromomagnetic (μ̂ t) moments have been measured using LHC pp collisions at a center-of-mass energy of 13 TeV, collected in the CMS detector in a data sample corresponding to an integrated luminosity of 35.9 fb−1. The linearized variable AFB(1) is used to approximate the asymmetry. Candidate t t ¯ events decaying to a muon or electron and jets in final states with low and high Lorentz boosts are selected and reconstructed using a fit of the kinematic distributions of the decay products to those expected for t t ¯ final states. The values found for the parameters are AFB(1)=0.048−0.087+0.095(stat)−0.029+0.020(syst),μ̂t=−0.024−0.009+0.013(stat)−0.011+0.016(syst), and a limit is placed on the magnitude of | d̂ t| < 0.03 at 95% confidence level. [Figure not available: see fulltext.

An embedding technique to determine ττ backgrounds in proton-proton collision data

An embedding technique is presented to estimate standard model tau tau backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed mu mu events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS. Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at root s = 13 TeV corresponding to an integrated luminosity of 41.5 fb(-1).Peer reviewe

Measurement of the Splitting Function in &ITpp &ITand Pb-Pb Collisions at root&ITsNN&IT=5.02 TeV

Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions, but it is not known where in the shower evolution the modifications occur. The momentum ratio of the two leading partons, resolved as subjets, provides information about the parton shower evolution. This substructure observable, known as the splitting function, reflects the process of a parton splitting into two other partons and has been measured for jets with transverse momentum between 140 and 500 GeV, in pp and PbPb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair. In central PbPb collisions, the splitting function indicates a more unbalanced momentum ratio, compared to peripheral PbPb and pp collisions.. The measurements are compared to various predictions from event generators and analytical calculations.Peer reviewe

Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe

MUSiC : a model-unspecific search for new physics in proton-proton collisions at root s=13TeV

Results of the Model Unspecific Search in CMS (MUSiC), using proton-proton collision data recorded at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1), are presented. The MUSiC analysis searches for anomalies that could be signatures of physics beyond the standard model. The analysis is based on the comparison of observed data with the standard model prediction, as determined from simulation, in several hundred final states and multiple kinematic distributions. Events containing at least one electron or muon are classified based on their final state topology, and an automated search algorithm surveys the observed data for deviations from the prediction. The sensitivity of the search is validated using multiple methods. No significant deviations from the predictions have been observed. For a wide range of final state topologies, agreement is found between the data and the standard model simulation. This analysis complements dedicated search analyses by significantly expanding the range of final states covered using a model independent approach with the largest data set to date to probe phase space regions beyond the reach of previous general searches.Peer reviewe