A Fast Active Set Block Coordinate Descent Algorithm for ℓ1\ell_1-regularized least squares

The problem of finding sparse solutions to underdetermined systems of linear equations arises in several applications (e.g. signal and image processing, compressive sensing, statistical inference). A standard tool for dealing with sparse recovery is the $\ell_1$-regularized least-squares approach that has been recently attracting the attention of many researchers. In this paper, we describe an active set estimate (i.e. an estimate of the indices of the zero variables in the optimal solution) for the considered problem that tries to quickly identify as many active variables as possible at a given point, while guaranteeing that some approximate optimality conditions are satisfied. A relevant feature of the estimate is that it gives a significant reduction of the objective function when setting to zero all those variables estimated active. This enables to easily embed it into a given globally converging algorithmic framework. In particular, we include our estimate into a block coordinate descent algorithm for $\ell_1$-regularized least squares, analyze the convergence properties of this new active set method, and prove that its basic version converges with linear rate. Finally, we report some numerical results showing the effectiveness of the approach.Comment: 28 pages, 5 figure

An Active-Set Algorithmic Framework for Non-Convex Optimization Problems over the Simplex

In this paper, we describe a new active-set algorithmic framework for minimizing a non-convex function over the unit simplex. At each iteration, the method makes use of a rule for identifying active variables (i.e., variables that are zero at a stationary point) and specific directions (that we name active-set gradient related directions) satisfying a new "nonorthogonality" type of condition. We prove global convergence to stationary points when using an Armijo line search in the given framework. We further describe three different examples of active-set gradient related directions that guarantee linear convergence rate (under suitable assumptions). Finally, we report numerical experiments showing the effectiveness of the approach.Comment: 29 pages, 3 figure

TE Wave Measurement and Modeling

In the TE wave method, microwaves are coupled into the beam-pipe and the effect of the electron cloud on these microwaves is measured. An electron cloud (EC) density can then be calculated from this measurement. There are two analysis methods currently in use. The first treats the microwaves as being transmitted from one point to another in the accelerator. The second more recent method, treats the beam-pipe as a resonant cavity. This paper will summarize the reasons for adopting the resonant TE wave analysis as well as give examples from CESRTA and DA{\Phi}NE of resonant beam-pipe. The results of bead-pull bench measurements will show some possible standing wave patterns, including a cutoff mode (evanescent) where the field decreases exponentially with distance from the drive point. We will outline other recent developments in the TE wave method including VORPAL simulations of microwave resonances, as well as the simulation of transmission in the presence of both an electron cloud and magnetic fields.Comment: Presented at ECLOUD'12: Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects, La Biodola, Isola d'Elba, Italy, 5-9 June 2012; CERN-2013-002, pp. 193-20

Productivity dynamics in Italy: learning and selection

This paper investigates the sources of labour productivity dynamics in Italy between 2011 and 2018. Exploiting the FRAME-SBS dataset maintained by Istat, we apply productivity decomposition methods to assess the relative contribution of within firm productivity (“learning” effect) and reallocation of market shares across firms (“market selection” effect) to aggregate productivity. While we cannot measure entry/exit dynamics and thus focus on incumbents, the comprehensive coverage of the Italian economy offered by the data enables us to perform a disaggregated analysis at the level of very narrowly defined industries (at 5-digit level, NACE Rev.2). This provides a significant contribution to the literature, as previous studies looked at aggregate economy or aggregate macro-sectors (e.g. total manufacturing). The general picture emerging from the analysis is that within-firm “learning” prevails over between-firm reallocation and allocative efficiency effects in shaping aggregate productivity dynamics. This finding is robust over time and across both manufacturing and service industries. In addition, allocative efficiency is generally stable and rather weak over the reference period, although somewhat stronger in manufacturing than in services

Analgesic effectiveness and tolerability of oral oxycodone/naloxone and pregabalin in patients with lung cancer and neuropathic pain. An observational analysis

INTRODUCTION: Cancer-related pain has a severe negative impact on quality of life. Combination analgesic therapy with oxycodone and pregabalin is effective for treating neuropathic cancer pain. We investigated the efficacy and tolerability of a dose-escalation combination therapy with prolonged-release oxycodone/naloxone (OXN-PR) and pregabalin in patients with non-small-cell lung cancer and severe neuropathic pain. METHODS: This was a 4-week, open-label, observational study. Patients were treated with OXN-PR and pregabalin. Average pain intensity ([API] measured on a 0-10 numerical rating scale) and neuropathic pain (Douleur Neuropathique 4) were assessed at study entry and at follow-up visits. The primary endpoint was response to treatment, defined as a reduction of API at T28 ≥30% from baseline. Secondary endpoints included other efficacy measures, as well as patient satisfaction and quality of life (Brief Pain Inventory Short Form), Hospital Anxiety and Depression Scale, and Symptom Distress Scale; bowel function was also assessed. RESULTS: A total of 56 patients were enrolled. API at baseline was 8.0±0.9, and decreased after 4 weeks by 48% (4.2±1.9; P<0.0001 vs baseline); 46 (82.1%) patients responded to treatment. Significant improvements were also reported in number/severity of breakthrough cancer pain episodes (P=0.001), Brief Pain Inventory Short Form (P=0.0002), Symptom Distress Scale (P<0.0001), Hospital Anxiety and Depression Scale depression (P=0.0006) and anxiety (P<0.0001) subscales, and bowel function (P=0.0003). At study end, 37 (66.0%) patients were satisfied/very satisfied with the new analgesic treatment. Combination therapy had a good safety profile. CONCLUSION: OXN-PR and pregabalin were safe and highly effective in a real-world setting of severe neuropathic cancer pain, with a high rate of satisfaction, without interference on bowel function

RELATIONSHIP BETWEEN OS ACROMIALE AND ACROMIOCLAVICOLAR JOINT ANATOMIC POSITION

Most of the orthopaedic literature on os acromiale is focused on the clinical implications, such as impingement and rotator cuff tears; although os acromiale is present in 8% of subjects, scarce information is reported on the causes that may predispose patients to it. Our aim is to investigate whether the origin of os acromiale is related to the position of the acromioclavicular (AC) joint. The acromions of 211 volunteers (control group) and 33 subjects without or with os acromiale were radiographically (axillary view) classified by the Edelson and Taitz method. The method distinguishes the acromion into three types on the basis of the distance between the anterior aspect of the acromion and the AC joint. Of 33 subjects with os acromiale, 11 were without pain. We have compared the frequency of the three types of acromion observed in the two investigated cohorts. Half of the acromions of the control group (52.1%) had the articular facet of the AC joint on the acromion tip, whereas in 45.4% the facet tip was located distally. On the other hand, of 33 subjects with os acromiale, 18.1% and 81.1%, respectively, had the AC joint lying on or distal to the acromion tip. Our data suggest that the greater the distance of the AC joint from the anterior edge of the acromion, the higher the likelihood of an os acromiale

The use of x-ray CT and MRI in the study of sacroiliac joints in patients with Behcet disease and acute anterior uveitis

Objective: It's controversial if Behcet Disease (BD) must be included in the group of seronegative spondyloarthropathy (SpA). Our aim was to establish the prevalence of sacroiliitis (SI) in patients with BD using X-Ray, CT and MRI, in comparison with patients with Acute Anterior Uveitis (AAU), that is known to belong to the subgroups of SpA. Methods: We considered, in the period from 04/2006 to 04/2009, 21 consecutive patients with BD, positive for HLA B51 and 28 consecutive patients with AAU, positive for HLA B27. These patients were previously selected by our Rheumatological Ward. Altogether we evaluated 98 sacroiliac joints (SIJ); each side of any patient was graded separately. Results: X-ray of the pelvis showed advanced SI (grade 4) in 14% of the cases in patients with AAU; in BD group only 7% CT showed advanced SI in 14% within AAU patients versus 6-12% of advanced SI (right to left) within BD patients. MR showed 14% of advanced SI (bilateral) within AAU versus 6-11% of advanced SI (right to left) in BD patients. Conclusions: This study supports the trend to not consider BD within the SpA, being the prevalence of SI in BD patients not very different from general population and anyway lower than that observed in patients with AAU. On the other side the prevalence of SI in AAU patients is higher than in BD patients and very similar to the one observed in patients with seronegative arthritis, and anyway high enough to consider joint involvement as an important feature of the disease