Intermittent accreting millisecond pulsars: light houses with broken lamps?

Intermittent accreting millisecond X-ray pulsars are an exciting new type of sources. Their pulsations appear and disappear either on timescales of hundreds of seconds or on timescales of days. The study of these sources add new observational constraints to present models that explain the presence or not of pulsations in neutron star LMXBs. In this paper we present preliminary results on spectral and aperiodic variability studies of all intermittent AMSPs, with a particular focus on the comparison between pulsating and non pulsating periods.Comment: 4 pages, 2 figures; to appear in the proceedings of the workshop "A Decade of Accreting Millisecond X-ray Pulsars", Amsterdam, April 2008, eds. R. Wijnands et al. (AIP Conf. Proc.

Mechanistic Insight into the Catechol Oxidase Activity by a Biomimetic Dinuclear Copper Complex

The biomimetic catalytic oxidation of 3,5-ditert- butylcatechol by the dicopper(II) complex of the ligand a,a¢-bis{bis[1-(1¢-methyl-2¢-benzimidazolyl) methyl]amino}-m-xylene in the presence of dioxygen has been investigated as a function of temperature and pH in a mixed aqueous/organic solvent. The catalytic cycle occurs in two steps, the first step being faster than the second step. In the first step, one molecule of catechol is oxidized by the dicopper(II) complex, and the copper(II) centers are reduced. From the pH dependence, it is deduced that the active species of the process is the monohydroxo form of the dinuclear complex. In the second step, the second molecule of catechol is oxidized by the dicopper(I)-dioxygen complex formed upon oxygenation of the reduced complex. In both cases, catechol oxidation is an inner-sphere electron transfer process involving binding of the catechol to the active species. The binary catechol-dicopper(II) complex formed in the first step could be characterized at very low temperature (90 C), where substrate oxidation is blocked. On the contrary, the ternary complex of dicopper( I)-O2-catechol relevant to the second step does not accumulate in solution and could not be characterized, even at low temperature. The investigation of the biphasic kinetics of the catalytic reaction over a range of temperatures allowed the thermodynamic (DH and DS) and activation parameters (DH „ and DS „ ) connected with the key steps of the catecholase process to be obtained

Tecniche di Network Anomaly Detection Multidimensionale

La continua diffusione delle tecnologie che permettono di trasmettere informazioni attraverso la rete Internet a velocità sempre maggiori e la costante crescita dell'impiego della rete stessa per fornire servizi rendono necessario lo sviluppo di tecniche sempre più veloci ed efficaci per la protezione da possibili attacchi informatici. In questa tesi focalizziamo l'attenzione sugli Intrusion Detection System (IDS), quei sistemi utilizzati per identificare attività dannose non autorizzate che hanno superato eventuali misure di prevenzione. In particolare vengono trattati sistemi che eseguono un'analisi statistica, con lo scopo di rilevare anomalie nell'andamento di parametri relativi al traffico di rete. L'obiettivo è quello di sviluppare nuovi IDS "multidimensionali", che monitorano contemporaneamente più serie temporali di dati con l'impiego di un unico algoritmo di change detection, per individuare intrusioni di tipo diverso. Dalle prove sperimentali eseguite, sono state ottenute prestazioni simili a quelle proprie di sistemi monodimensionali applicati separatamente a ciascuna sequenza analizzata: il nuovo approccio dimostra quindi vantaggi in termini di costo computazionale

Total Parathyroidectomy with Subcutaneous Parathyroid Forearm Autotransplantation in the Treatment of Secondary Hyperparathyroidism: A Single-Center Experience.

Abstract Introduction Secondary hyperparathyroidism is common in chronic kidney disease. Parathyroidectomy is indicated in refractory hyperparathyroidism when medical treatments and so the parathyroid hormone levels cannot be lowered to acceptable values without causing significant hyperphosphatemia or hypercalcemia. The aim of this study is to compare the efficacy and safety of total parathyroidectomy with subcutaneous forearm autotransplantation with total parathyroidectomy with intramuscular forearm autotransplantation. Materials and Methods A single-center retrospective cohort study of total parathyroidectomy with forearm autotransplantation from January 2002 to February 2013 was performed. According to the surgical technique, patients were divided into an intramuscular group (Group 1) and a subcutaneous group (Group 2). 38 patients with secondary hyperparathyroidism were enrolled; 23 patients were subjected to total parathyroidectomy with parathyroid tissue replanting in the subcutaneous forearm of the upper nondominant limb, while 15 patients were subjected to replanting in the intramuscular seat. Results A total of 38 patients (56 ± 13 years) were enrolled. In both groups, the preoperative iPTH value was markedly high, 1750 ± 619 pg/ml in the intramuscular autotransplantation group and 1527 ± 451 pg/ml in the subcutaneous autotransplantation group (p = 0.079). Transient hypoparathyroidism was shown in 7 patients, and 1 patient showed persistent hypoparathyroidism (p = 0.387). 2 patients showed persistent hyperparathyroidism (p = 0.816), and in 2 others was found recurrent hyperparathyroidism (p = 0.816); 3 of them underwent autograftectomy. The anterior compartment of the forearm nondominant limb was sacrificed in 1 case of intramuscular autotransplantation with functional arm deficit. Conclusions The efficacy and safety of parathyroid tissue autotransplantation in the subcutaneous forearm of the upper nondominant limb is confirmed with a good rate of tissue engraftment and with a comparable number of postsurgical transient and persistent hypoparathyroidism and hyperparathyroidism incidence in both techniques. Furthermore, this technique preserves arm functionality in the case of autograftectomy. Consequently, it is our opinion that total parathyroidectomy with subcutaneous forearm autotransplantation is currently the best choice

The effects of match-playing aspects and situational variables on achieving score-box possessions in Euro 2012 Football Championship

The aim of this study was to examine the independent and interactive effects of several match-playing aspects and situational variables on the probability of achieving score-box possessions in the 2012 European Championship. The non-clinical magnitude-based inferences method was used to interpret the true effect of the performance indicators on the response variable. The logistic regression analysis in univariate perspective showed that the probability of achieving score-box possessions was greater in the second half than in the first (OR: 1.23, P<0.05, very likely positive effect), but it was lower when a team performed a direct attack rather than a possession play (OR: 0.49, P< 0.001, most likely negative effect), when the possession started in the right path of the field than in the left (OR: 0.69, P < 0.01, most likely negative effect), and when a team played against highest ranked team (from very to most likely negative effect). In multivariate perspective, the negative effect of the direct attack to the probability of achieving score-box possessions was confirmed, and an interactive effect showed that this outcome was greater in the knockout phase of the tournament than in the relative group-stage (OR: 0.62, P< 0.05, very likely negative effect)

Timing the accretion flow around accreting millisecond pulsars

At present, ten years after they were first discovered, ten accreting millisecond pulsars are known. I present a study of the aperiodic X-ray variability in three of these systems, which led to the discovery of simultaneous kHz quasi periodic oscillations in XTE J1807-294 and extremely strong broadband noise at unusually low variability frequencies in IGR J00291+5934. Furthermore, we classified SWIFT J1756.9-2508 as an atoll source and measured in its 2007 outburst spectral and variability properties typical of the extreme island state. I also give detailed estimates of the total fluence during the studied outbursts.Comment: To be published in the proceedings of the workshop 'A Decade of Accreting Millisecond X-ray pulsars' (Amsterdam 14-18 April 2008; Eds. Wijnands et al.

Modelling the outburst profile of X-ray powered millisecond pulsars

The outbursts of low mass X-ray binaries are prolonged relative to those of dwarf nova cataclysmic variables as a consequence of X-ray irradiation of the disc. We show that the time-scale of the decay light curve and its luminosity at a characteristic time are linked to the radius of the accretion disc. Hence a good X-ray light curve permits two independent estimates of the disc radius. In the case of the millisecond pulsars SAX J1808.4-3658 and XTE J0929-314 the agreement between these estimates is very strong. Our analysis allows new determinations of distances and accretion disc radii. Our analysis will allow determination of accretion disc radii for sources in external galaxies, and hence constrain system parameters where other observational techniques are not possible. We also use the X-ray light curves to estimate the mass transfer rate. The broken exponential decay observed in the 2002 outburst of SAX J1808.4-3658 may be caused by the changing self-shadowing of the disc.Comment: To be published in the proceedings of the workshop 'A Decade of Accreting Millisecond X-ray pulsars' (Amsterdam 14-18 April 2008; Eds. Wijnands et al.

Modeling pulse profiles of accreting millisecond pulsars

I review the basic observational properties of accreting millisecond pulsars that are important for understanding the physics involved in formation of their pulse profiles. I then discuss main effects responsible for shaping these profiles. Some analytical results that help to understand the results of simulations are presented. Constraints on the pulsar geometry and the neutron star equation of state obtained from the analysis of the pulse profiles are discussed.Comment: Invited review, to appear in the proceedings of the workshop 'A Decade of Accreting Millisecond X-ray Pulsars' (Amsterdam, April 2008

The Spin Distribution of Millisecond X-ray Pulsars

The spin frequency distribution of accreting millisecond X-ray pulsars cuts off sharply above 730 Hz, well below the breakup spin rate for most neutron star equations of state. I review several different ideas for explaining this cutoff. There is currently considerable interest in the idea that gravitational radiation from rapidly rotating pulsars might act to limit spin up by accretion, possibly allowing eventual direct detection with gravitational wave interferometers. I describe how long-term X-ray timing of fast accreting millisecond pulsars like the 599 Hz source IGR J00291+5934 can test the gravitational wave model for the spin frequency limit.Comment: 8 pages with 2 figures, to appear in the proceedings of "A Decade of Accreting Millisecond X-ray Pulsars", Amsterdam, April 2008, eds. R. Wijnands et al. (AIP Conf. Proc.

Lighthouses with two lights: burst oscillations from the accretion-powered millisecond pulsars

The key contribution of the discovery of nuclear-powered pulsations from the accretion-powered millisecond pulsars (AMPs) has been the establishment of burst oscillation frequency as a reliable proxy for stellar spin rate. This has doubled the sample of rapidly-rotating accreting neutron stars and revealed the unexpected absence of any stars rotating near the break-up limit. The resulting `braking problem' is now a major concern for theorists, particularly given the possible role of gravitational wave emission in limiting spin. This, however, is not the only area where burst oscillations from the AMPs are having an impact. Burst oscillation timing is developing into a promising technique for verifying the level of spin variability in the AMPs (a topic of considerable debate). These sources also provide unique input to our efforts to understand the still-elusive burst oscillation mechanism. This is because they are the only stars where we can reliably gauge the role of uneven fuel deposition and, of course, the magnetic field.Comment: Invited review, to appear in the proceedings of the workshop 'A decade of accreting millisecond x-ray pulsars' (Amsterdam, April 2008