Magnetic ordering in strong anisotropic ferromagnetic bilayers with dipolar and antiferromagnetic interlayer exchange interactions: Monte Carlo approach.

In this work, multilayer films consisting of two strong-anisotropic ferromagnetic layers antiferromagnetically coupled by a nonmagnetic spacer are studied by Monte Carlo simulations. The system is modeled by an Ising-based Hamiltonian that depends on both the intralayer exchange and dipolar constants and on the interlayer exchange constant (IEC). The ground state of the monolayers (null IEC) corresponds to alternate stripe domains with width h defined by the ratio between the exchange and dipolar constants (δ). The results show that IEC alters the energy balance that controls the stripe domain formation, leading to a ground state characterized by in-plane stripes out-plane antiferromagnetically coupled. When temperature increases two regimes are identified: an IEC-dominated regime where the orientational and positional orders are simultaneously lost in both layers, driving the system to the tetragonal liquid (TL) phase, and a dipolar-dominated one where signs of layers decoupling and the onset of positional disorder are observed. The last could be related with an intermediate nematic phase (NM). From the study of the nonequilibrium dynamics, the phase transitions to TL phase are characterized as continuous and those to the NM one as Kosterlitz-Thouless type. Also, for both layers the critical temperatures are the same and increase with IEC magnitude. Furthermore, the obtained critical exponents depend on the IEC values, which is indicative of a weak universality. For the dipolar-dominated regime, the decoupling between layers is also evidenced by the difference between their critical exponents.

Environmental electroactive consortia as reusable biosensing element for freshwater toxicity monitoring.

The development of tools to monitor water quality is mandatory in a scenario where clean water resources are decreasing. Here, the biosensing capability of an electroactive river sediment consortium was tested towards three model contaminants (glutaraldehyde, nickel(II) and chromium(III)). The proposed biosensor is a small membrane-less single chamber Microbial Fuel Cell (MFC), fabricated by 3D printing. Its semi-continuous mode of operation resulted in long-term current profile stability and reproducibility. A linear trend of response was obtained for glutaraldehyde in a concentration range of 5-1000 ppm. After the recovery of the electroactive consortium activity, the MFC-based biosensors were shown to be sensitive towards Ni(II) and Cr(III), at concentrations above 2 mg L-1. To effectively analyze biosensor response, a novel algorithm was proposed, offering advantages for the realization of energy-saving protocols for MFC-biosensor data transmission. Implementation of the device and method, from laboratory test to real environment, can offer a low cost in situ system for detection of water contaminants.

Evidence of Kosterlitz-Thouless phase transitions in the Ising model with dipolar interactions.

The ferromagnetic bidimensional Ising model with dipolar interactions has been proposed to model ultrathin films with strong out-of-plane anisotropy. The phase diagram presents a rich phenomenology that includes low-temperature phases characterized by stripes of width n (h_{n}) and a high-temperature phase with domains of stripes with mutually perpendicular orientations, named tetragonal liquid (TL). The latter phase can be reached by two possible ways. One of them is the direct transition h_{n} to TL, and the other one is through an intermediate phase with orientational order but short-range positional disorder, named nematic phase (NM). The regions of the phase diagram where these transitions occur, as well as their character, remain an open question and are the object of the present work. In order to clarify this topic, intensive Monte Carlo simulations were performed by employing short-time dynamics as the main tool for studying the phase transition behavior. The dynamic evolution of the orientational order parameter and its moments are measured for selected values of the ratio between the ferromagnetic exchange and dipolar constants, called δ. The obtained results indicate that the intermediate NM phase is present for δ≥2 in narrow ranges of temperatures. Also, the results suggest that both transitions, i.e., h_{n}-NM and NM-TL, have a Kosterlitz-Thouless character. This type of topological transition is observed in continuous bidimensional models and have been proposed for discrete ones, as in the case of the present work.

Nanoclusters of crystallographically aligned nanoparticles for magnetic thermotherapy: aqueous ferrofluid, agarose phantoms and ex vivo melanoma tumour assessment.

Magnetic hyperthermia is an oncological therapy where magnetic nanostructures, under a radiofrequency field, act as heat transducers increasing tumour temperature and killing cancerous cells. Nanostructure heating efficiency depends both on the field conditions and on the nanostructure properties and mobility inside the tumour. Such nanostructures are often incorrectly bench-marketed in the colloidal state and using field settings far off from the recommended therapeutic values. Here, we prepared nanoclusters composed of iron oxide magnetite nanoparticles crystallographically aligned and their specific absorption rate (SAR) values were calorimetrically determined in physiological fluids, agarose-gel-phantoms and ex vivo tumours extracted from mice challenged with B16-F0 melanoma cells. A portable, multipurpose applicator using medical field settings; 100 kHz and 9.3 kA m-1, was developed and the results were fully analysed in terms of nanoclusters' structural and magnetic properties. A careful evaluation of the nanoclusters' heating capacity in the three milieus clearly indicates that the SAR values of fluid suspensions or agarose-gel-phantoms are not adequate to predict the real tissue temperature increase or the dosage needed to heat a tumour. Our results show that besides nanostructure mobility, perfusion and local thermoregulation, the nanostructure distribution inside the tumour plays a key role in effective heating. A suppression of the magnetic material effective heating efficiency appears in tumour tissue. In fact, dosage had to be increased considerably, from the SAR values predicted from fluid or agarose, to achieve the desired temperature increase. These results represent an important contribution towards the design of more efficient nanostructures and towards the clinical translation of hyperthermia.

Severe ulcerative colitis: predictors of response and algorithm proposal for rescue therapy.

BACKGROUND: There is no agreeing if rescue therapy can avoid short-term colectomy in patients treated for severe steroid-refractory ulcerative colitis. AIMS: The aim of our study was to identify predictors of response to infliximab and cyclosporine A. METHODS: In this cross-sectional study, 49 patients with severe ulcerative colitis were included. Response to therapy was defined as three or more point reductions in Mayo score after 6 months of treatment and avoidance of colectomy after 1 year. The predictors analysed were gender, age, time from ulcerative colitis diagnosis, months of steroid or/and azathioprine therapy before onset of the severe phase, smoking habits, extension of the disease, laboratory analyses and Mayo score. RESULTS: Patients treated with infliximab showed a statistically significant higher response rate in case of moderate Mayo score (P = 0.04). Ex-smokers had very low chance of response to infliximab (P = 0.03). In the group treated with cyclosporine A, patients with C-reactive protein >3 mg/L had a response rate significantly higher than those with C-reactive protein <3 mg/L (P = 0.03); those with negative C-reactive protein and moderate Mayo score did not responded to therapy, while in the ones with elevated C-reactive protein and/or severe Mayo score, 15 versus 4 responded (P = 0.008). CONCLUSIONS: Our data suggest that cyclosporine A is advisable in ex-smokers. In never smokers or active smokers, infliximab can be prescribed in case of Mayo score ≤10 and/or negative CRP, while cyclosporine A is indicated in case of Mayo score >10 and positive CRP.

Pathogenesis of chronic cluster headache and bouts: role of tryptamine, arginine metabolism and α1-agonists.

The aim of this study was to explore the possible role of tryptamine in the pathogenesis of chronic cluster headache along with that of adrenaline and noradrenaline (α-agonists) together with arginine metabolism in the origin of cluster bouts. Plasma levels of tyramine, tryptamine, serotonin, 5-hydroxyindolacetic acid, noradrenalin, adrenalin and the markers of arginine metabolism such as arginine, homoarginine, citrulline, ADMA and NMMA, were measured in 23 chronic cluster headache patients (10 chronic cluster ab initio and 13 transformed from episodic cluster) and 28 control subjects. The plasma levels of tyramine, tryptamine, noradrenalin and adrenalin were found several times higher in chronic cluster headache patients compared to controls, whereas the plasma levels of arginine, homoarginine and citrulline were significantly lower. No differences were found in the plasma levels of serotonin, 5-hydroxyindolacetic, ADMA and NMMA between chronic cluster headache patients and control subjects. These results provide support for a role of tryptamine in the pathogenesis of chronic cluster headache and, in particular, in the duration of the cluster bouts. In addition, the low levels of the nitric oxide substrates together with the high levels of noradrenalin and adrenalin suggest an activation of endothelial TAAR1 receptors followed by the release of nitric oxide in the circulation that may constitute the final step of the physiopathology of cluster crisis.

Phase transitions and multicritical behavior in the Ising model with dipolar interactions.

In this work, the phase diagram of the ferromagnetic Ising model with dipole interactions is revisited with the aim of determining the nature of the phase transition between stripe-ordered phases with width n (h_{n}) and tetragonal liquid (TL) phases. Extensive Monte Carlo simulations are performed in order to study the short-time dynamic behavior of the observables for selected values of the ratio between the ferromagnetic exchange and dipolar constants δ. The obtained results indicate that the h_{1}-TL phase transition line is continuous up to δ=1.2585, while for the h_{2}-TL line a weak first-order character is found in the interval 1.2585≤δ≤1.36 and becomes continuous for 1.37≤δ≤1.9. This result suggests the existence of a tricritical point close to δ=1.37. When it is appropriate, the complete set of critical exponents is obtained, and in all the studied cases they depend on δ but do not belong to the Ising universality class. Furthermore, short-time dynamic studies reveal that at the point where the mentioned lines meet the h_{1}-h_{2} line, i.e., at δ=1.2585, the critical phase corresponding to the h_{1}-TL transition coexists with the h_{2} phase.

Phase transitions and critical phenomena in the two-dimensional Ising model with dipole interactions: A short-time dynamics study.

The ferromagnetic Ising model with antiferromagnetic dipole interactions is investigated by means of Monte Carlo simulations, focusing on the characterization of the phase transitions between the tetragonal liquid and stripe of width h phases. The dynamic evolution of the physical observables is analyzed within the short-time regime for 0.5≤δ≤1.3, where δ is the ratio between the short-range exchange and the long-range dipole interaction constants. The obtained results for the interval 0.5≤δ≤1.2 indicate that the phase transition line between the h=1 stripe and tetragonal liquid phases is continuous. This finding contributes to clarifying the controversy about the order of this transition. This controversy arises from the difficulties introduced in the simulations due to the presence of long-range dipole interactions, such as an important increase in the simulation times that limits the system size used, strong finite size effects, as well as to the existence of multiple metastable states at low temperatures. The study of the short-time dynamics of the model allows us to avoid these hindrances. Moreover, due to the fact that the finite-size effects do not significantly affect the power-law behavior exhibited in the observables within the short-time regime, the results could be attributed to those corresponding to the thermodynamic limit. As a consequence of this, a careful characterization of the critical behavior for the whole transition line is performed by giving the complete set of critical exponents.

Benefit of supplements in functional dyspepsia after treatment of Helicobacter pylori.

AIM: Functional dyspepsia, though benign, leads to deterioration of the quality of life and high costs for healthcare systems. The optimal therapy for functional dyspepsia is still to be defined because of its multifactorial pathogenesis. In an open multicentric study of patients with functional dyspepsia, we prospectively evaluated the benefit of treatment with a food supplement composed of sodium alginate, carbonate calcium, pineapple, papaya, ginger, α-galactosidase and fennel (Perdiges, Bioten Snc, Turin, Italy). METHODS: Ninety-one consecutive patients were included, suffering from functional dyspepsia, who had been previously submitted to therapy to eradicate the infection from Helicobacter pylori (H. pylori) and were waiting to perform the Urea Breath Test (UBT). The primary goal was to establish the percentage of patients who continued to abstain from proton pump inhibitors (PPI) as they waited to carry out the UBT, differentiating between patients who were treated (N.=55) with Perdiges and those who were not (N.=36). Our secondary goal was to document the differences within the 2 groups in terms of symptoms perceived between the start and end of the observation period. The wellness reported, during or in absence of treatment with Perdiges, was evaluated by the use of the VAS scale (Visual Analogical Scale) completed before the start of the treatment and after 30 days. RESULTS: All the patients treated with Perdiges (55/55, 100%) and 31/36 (86.1%) patients who were not (P=0.008) continued to abstain from PPI in the period awaiting the UBT. The VAS scale of those who took Perdiges improved on average by 1.78 points versus a worsening of 0.08 points of those who did not take it (P<0.0001). Furthermore, while among those who took Perdiges there was a statistically significant improvement (P<0.0001) in the VAS scale, between the baseline and the end of treatment, a worsening of 0.08 points (P=0.78) was noticed among the patients who did not take it. CONCLUSION: Perdiges is significantly effective in the period following treatment to eradicate the infection from H. pylori in patients with functional dyspepsia. This allows to reduce the need to use antisecretive drugs. Further randomised studies, with wide ranging case histories, must assess its long-term efficacy.

Helicobacter pylori infection and diabetes mellitus: the 2013 state of art.

It is well-known the role of Helicobacter pylori (H. pylori) infection in the development of gastroduodenal diseases. From two decades literature has suggested the potential relationship of the bacterium with extragastric manifestations. Aim of the present review was to analyze the consistency of a potential involvement of H. pylori infection in the pathogenesis of diabetes mellitus (DM) as well as in the gastric abnormalities associated with this disease. Several studies reported a higher prevalence of H. pylori infection in diabetic patients with or without dyspeptic symptoms than in controls and a positive association with insulin resistance (IR) has been shown. However, DM has a multifactorial pathogenesis and the detection of the role of each agent is difficult. The different factors implicated in the development of DM as well as of IR include inflammation, autoimmunuty, stimulation of innate immune system, trigger to platelet activation and platelet-leukocyte aggregation, action on leptin and ghrelin regulation, alterated lipid metabolism and insulin sensitivity. Effectiveness of H. pylori eradication results significantly lower in diabetic patients than in controls, most likely because of the large use of antibiotic in DM subjects, causing selection of resistant H. pylori strains. Finally, re-infection after bacterial eradication, although rarely observed in the general population, seems to be more frequent in diabetic patients than in controls.

Shearing self-propelled suspensions: arrest of coarsening and suppression of giant density fluctuations.

We study the effect of a linear shear flow on a collection of interacting active, self-propelled particles modeled via the Vicsek model. The imposed flow has a dramatic effect on the behavior of the model. We find that in the presence of shear there is no order-disorder transition, and that coarsening of the domains is arrested. Shear also suppresses the so-called giant density fluctuations that are observed in the quiescent limit.

Molecular findings on Helicobacter pylori: update for clinicians.

Helicobacter pylori (H. pylori) is a gram-negative bacterium which is responsible for a wide range of disorders of the stomach, from chronic gastritis to peptic ulcers to gastric cancer which, however, occurs in a lower percentage of subjects. The difference in the clinical course of infection seems to be correlated both to the typical pathogenicity of the bacterium and to factors related to the host. The reasons underlying these observations include differences in bacterial pathogenicity as well as in host susceptibility. Numerous studies published in the last year have provided new insights into H. pylori virulence factors, their interaction with the host and the relative consequences in the pathogenesis. In this review, we have set ourselves the target of summarising the latest progress made in understanding the molecular aspects of H. pylori infection of notable importance for the physician.

Endoscopic banding for esophageal variceal bleeding: technique and patient outcome.

AIM: Endoscopic variceal ligation (EVL) is recommended for the treatment of esophageal variceal bleeding. The aim of this study was to assess the most cost-effective timing of endoscopic follow-up after variceal eradication. METHODS: Cirrhotics with esophageal varices treated between January 2008 and January 2009 until reached variceal obliteration were retrospectively analyzed for technical aspects and for outcomes. RESULTS: Out of 127 patients treated with EVL, 103 were included. Number of sessions to achieve variceal obliteration and number of bands for each session were 2.8±1.3 (range 1-7) and 4.6±1 (range 2-7), respectively. The placement of >5 bands per session was not associated with higher incidence of complications (19.6% vs. 17.8%, P=ns). Esophageal ulcers were observed in 42% of patients when the interbanding interval was <20 days (versus 15% for interval >20 days, P<0.05). Once obliteration was achieved, varices reappeared in 28% of patients; the early appearance of small varices was not associated with bleeding. CONCLUSION: A longer interbanding interval reduces the incidence of procedural-related complications. After variceal obliteration an early endoscopic control is not useful because it does not influence the approach and does not change the patient outcome.

Endoscopic retrograde cholangiopancreatography in patients with biliary complications after orthotopic liver transplantation: outcomes and complications.

Biliary complications after orthotopic liver transplantation (OLT) still remain a major cause of morbidity and mortality. The most frequent complications are strictures and leakages in OLT cases with duct-to-duct biliary reconstruction (D-D), which can be treated with dilatation or stent placement during endoscopic retrograde cholangiopancreatography (ERCP), although this procedure is burdened with potentially severe complications, such as retroperitoneal perforation, acute pancreatitis, septic cholangitis, bleeding, recurrence of stones, strictures due to healing process. The aim of the study was to analyze the outcome of this treatment and the complications related to the procedure. Among 1634 adult OLTs, we compared postprocedural complications and mortality rates with a group of 5852 nontransplanted patients (n-OLTs) who underwent ERCP. Of 472 (28,8%) post-OLT biliary complications, 319 (67.6%) occurred in D-D biliary anstomosis cases and 94 (29.5%) patients underwent 150 ERCP sessions. Among 49/80 patients (61.2%) who completed the procedure, ERCP treatment was successful. Overall complication rate was 10.7% in OLT and 12.8% in n-OLT (P = NS). Compared with the n-OLT group, post-ERCP bleeding was more frequent in OLT (5.3% vs 1.3%, P = .0001), while the incidence of pancreatitis was lower (4.7% vs 9.6%, P = .04). Procedure-related mortality rate was 0% in OLT and 0.1% in n-OLT (P = NS). ERCP is a safe procedure for post-OLT biliary complications in the presence of a D-D anastomosis. Morbidity and mortality related with this procedure are acceptable and similar to those among nontransplanted population.