The secret santa problem.

Consider a digraph where the vertices represent people and an arc (i, j) represents the possibility of i giving a gift to j. The basic question we pose is whether there is an anonymity-preserving “gift assignment” such that each person makes and receives exactly one gift, and such that no person i can infer the remaining gift assignments from the fact that i is assigned to give a gift to j. We formalize this problem as a graph property involving vertex disjoint circuit covers, give a polynomial algorithm to decide this property for any given graph and provide a computational validation of the algorithm

Simulation Studies of the NLC with Improved Ground Motion Models

The performance of various systems of the Next Linear Collider (NLC) have been studied in terms of ground motion using recently developed models. In particular, the performance of the beam delivery system is discussed. Plans to evaluate the operation of the main linac beam-based alignment and feedback systems are also outlined.Comment: Submitted to XX International Linac Conferenc

Inverse Spin Hall Effect and Anomalous Hall Effect in a Two-Dimensional Electron Gas

We study the coupled dynamics of spin and charge currents in a two-dimensional electron gas in the transport diffusive regime. For systems with inversion symmetry there are established relations between the spin Hall effect, the anomalous Hall effect and the inverse spin Hall effect. However, in two-dimensional electron gases of semiconductors like GaAs, inversion symmetry is broken so that the standard arguments do not apply. We demonstrate that in the presence of a Rashba type of spin-orbit coupling (broken structural inversion symmetry) the anomalous Hall effect, the spin Hall and inverse spin Hall effect are substantially different effects. Furthermore we discuss the inverse spin Hall effect for a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit coupling; our results agree with a recent experiment.Comment: 5 page

Combinatorial optimization based recommender systems.

Recommender systems exploit a set of established user preferences to predict topics or products that a new user might like [2]. Recommender systems have become an important research area in the field of information retrieval. Many approaches have been developed in recent years and the interest is very high. However, despite all the efforts, recommender systems are still in need of further development and more advanced recommendation modelling methods, as these systems must take into account additional requirements on user preferences, such as geographic search and social networking. This fact, in particular, implies that the recommendation must be much more “personalized” than it used to be. In this paper, we describe the recommender system used in the “DisMoiOu”(“TellMeWhere” in French) on-line service (http://dismoiou.fr), which provides the user with advice on places that may be of interest to him/her; the definition of “interest” in this context is personalized taking into account the geographical position of the user (for example when the service is used with portable phones such as the Apple iPhone), his/her past ratings, and the ratings of his/her neighbourhood in a known social network. Using the accepted terminology [6], DisMoiOu is mainly a Collaborative Filtering System (CFS): it employs opinions collected from similar users to suggest likely places. By contrast with existing recommender systems, ours puts together the use of a graph theoretical model [4] and that of combinatorial optimization methods [1]. Broadly speaking, we encode known relations between users and places and users and other users by means of weighted graphs. We then define essential components of the system by means of combinatorial optimization problems on a reformulation of these graphs, which are finally used to derive a ranking on the recommendations associated to pairs (user,place). Preliminary computational results on the three classical evaluation parameters for recommender systems (accuracy, recall, precision [3]) show that our system performs well with respect to accuracy and recall, but precision results need to be improved

Stratification of THROMBOTIC RISK in patients that are undergoing to PICC implantation. The “CoRa-MaPiCC STUDY”

Background: The PICC is a central venous system inserted in the peripherally vein. The central peripheral catheter catheter system (PICC=peripherally inserted central catheters) is a widely used procedure in clinical practice by medical and nurse team. PICC has potential complications that are rare but not entirely irrelevant. It is used for continuous and discontinuous treatment and, after a correct insertion procedure, it can be used for a period of time between 1 week to 3 months. The last-generation dispositive has an high-biocompatibility due to the high quality of the materials (silicone or polyurethane), a total length of 40-60 cm and a diameter between 16 to 25 Gauge or 2 to 5 French. Aims: The aim of our study is to evaluate the trombotic risk related to the positioning of the device in relation to the individual risk factors. Therefore we have elaborated the CoRaMaPicc protocol that allows, based on the preliminary data evaluation, to reduce the trombotic risk in patients with high cardiovascular risk profile. Methods: The study has started in July 2016. We have enrolled 30 patients (18 males and 12 females with range age of 30-99 yrs and mean age of 82+13,5 yrs). Enrolled patients have Body mass Index or (BMI) with range from 16,3-26,5 Kg/mq and mean BMI value of 23,5+2,5 Kg/mq. Enrolled patients were subjected to laboratory assessment of cardiovascular risk factors like laboratory assessment of Methyl-Tetra-Hydro-Folate-Reductase or (MTHFR) and Homocysteine, Fibrinogen, D-Dimer, International Normalized Ratio (INR), Prothrombin Time (PT), activated Partial Thromboplastin Time (aPTT), Platelets (PLT), trombotic risk evaluation (CHA2DS2-VASc Score), and bledding risk evaluation (HAS-BLED Score). Before the insertion procedure of the PICC, single or duble lumen (Groshong or Power PICC type), the patient were subjected to a preliminary ultrasound and echo-doppler vein evaluation to underline the presence of atipical anatomical state of the patients veins. After the procedure the patients were subjected to second ultrasound and echo-doppler vein evaluation and then to a radiographic examination to verify the correct position of the PICC. All patients were enrolled for follow- Up to evaluate trombotic complications. Statistical analysis was performed using the Survival Analysis test to evaluate the patients during the follow-up period in relation to thrombotic events. The data obtained from our study have been described taking also into account the data present in the international literature. Setting: The study was performed using a specific setting in a room of the Internal Medicine Department of the Alfredo Fiorini Hospital (Terracina, Italy), guarantee an aseptic procedure , the right comfort for the patients and the appropriate privacy. Discussion: More data in the literature underline the presence of non-eliminable risk factors like anatomic state of the patients vein that can play a variable role of procedural risk factor and can predispose to procedural or post-procedural complication after the implantation procedure. In specific cases it is difficult to asses an echo-doppler examination of heart for meteorism or ascites and radiographic exams for the presence of pleural effusion. The CoRaMaPiCC protocol use different technique to explore the post-insertion period and the follow-up time at 12 week. In case of meteorism or ascites the ultrasound examination of the heart cameras was replaced by the radiographyc evaluation while in case of pleural effusion, the evaluation of the device position was deduced using the only ultrasound approach (when the vein system is explorable). Procedural algorithm utilized in our implant protocol allows to improve the diagnostic capabilities of the conditions that can predispose to thrombotic complications. During the study period (1 year), the PICCs were removed for death (7 patients; 4 patients for irreversible heart disease, 1 patient for cardiogenic shock 1 patient for septic shock and 1 patient for Creutzfeld-Jacob disease), for spontaneously remotion (1 patient for low compliance of the patient) and for end of therapy (22 patients). The presence of cardiovascular risk factors alone is not sufficient for determining statistically significant changes in the thrombotic risk. As reported historically by the description of the wirkow triad, the presence of three clinical signs, and in particular the presence of endothelial damage (functio lesa) is a sine qua non condition for the occurrence of thrombotic episodes. Conclusion: The CoRaMaPicc protocol allows, based on the evaluation of the data, to minimize endothelial damage and therefore to reduce the incidence of the wirchof's triade related with an high trombotic risk. The data were elaborated considering the different thrombotic risk linked to the presence of the homozygous MTHR mutation responsible for the increase of homocysteine values and therefore of the further thrombotic risk. Further studies are needed to expand the number of enrolled patients and increase the follow-up period. Our data give comfortable results but further evaluation are needed to have conclusive results

Beam-based Feedback Simulations for the NLC Linac

Extensive beam-based feedback systems are planned as an integral part of the Next Linear Collider (NLC) control system. Wakefield effects are a significant influence on the feedback design, imposing both architectural and algorithmic constraints. Studies are in progress to assure the optimal selection of devices and to refine and confirm the algorithms for the system design. We show the results of initial simulations, along with evaluations of system response for various conditions of ground motion and other operational disturbances.Comment: 3 pages. Linac2000 conferenc