Low field hysteresis in disordered ferromagnets

We analyze low field hysteresis close to the demagnetized state in disordered ferromagnets using the zero temperature random-field Ising model. We solve the demagnetization process exactly in one dimension and derive the Rayleigh law of hysteresis. The initial susceptibility a and the hysteretic coefficient b display a peak as a function of the disorder width. This behavior is confirmed by numerical simulations d=2,3 showing that in limit of weak disorder demagnetization is not possible and the Rayleigh law is not defined. These results are in agreement with experimental observations on nanocrystalline magnetic materials.Comment: Extended version, 18 pages, 5 figures, to appear in Phys. Rev.

Canagliflozin and heart failure in Type 2 diabetes mellitus: results from the CANVAS Program (Canagliflozin Cardiovascular Assessment Study)

BACKGROUND : Canagliflozin is a sodium glucose cotransporter 2 inhibitor that reduces the risk of cardiovascular events. We report the effects on heart failure and cardiovascular death overall, in those with and without a baseline history of heart failure, and in other participant subgroups. METHODS : The CANVAS Program (Canagliflozin Cardiovascular Assessment Study) enrolled 10 142 participants with type 2 diabetes mellitus and high cardiovascular risk. Participants were randomly assigned to canagliflozin or placebo and followed for a mean of 188 weeks. The primary end point for these analyses was adjudicated cardiovascular death or hospitalized heart failure. RESULTS : Participants with a history of heart failure at baseline (14.4%) were more frequently women, white, and hypertensive and had a history of prior cardiovascular disease (all P0.130), except for a possibly reduced absolute rate of events attributable to osmotic diuresis among those with a prior history of heart failure (P=0.03). CONCLUSIONS : In patients with type 2 diabetes mellitus and an elevated risk of cardiovascular disease, canagliflozin reduced the risk of cardiovascular death or hospitalized heart failure across a broad range of different patient subgroups. Benefits may be greater in those with a history of heart failure at baseline. CLINICAL TRIAL REGISTRATION : URL: https://www.clinicaltrials.gov. Unique identifiers: NCT01032629 and NCT01989754

Canagliflozin for primary and secondary prevention of cardiovascular events: results from the CANVAS Program (Canagliflozin Cardiovascular Assessment Study)

BACKGROUND : Canagliflozin is a sodium glucose cotransporter 2 inhibitor that significantly reduces the composite of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke in patients with type 2 diabetes mellitus and elevated cardiovascular risk. The comparative effects among participants with and without a history of cardiovascular disease (secondary versus primary prevention) were prespecified for evaluation. METHODS : The CANVAS Program (Canagliflozin Cardiovascular Assessment Study) randomly assigned 10 142 participants with type 2 diabetes mellitus to canagliflozin or placebo. The primary prevention cohort comprised individuals ≥50 years of age with ≥2 risk factors for cardiovascular events but with no prior cardiovascular event, and the secondary prevention cohort comprised individuals ≥30 years of age with a prior cardiovascular event. The primary end point was a composite of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke. Secondary outcomes included heart failure hospitalization and a renal composite (40% reduction in estimated glomerular filtration rate, renal replacement therapy, or renal death). RESULTS : Primary prevention participants (N=3486; 34%) were younger (63 versus 64 years of age), were more often female (45% versus 31%), and had a longer duration of diabetes mellitus (14 versus 13 years) compared with secondary prevention participants (N=6656; 66%). The primary end point event rate was higher in the secondary prevention group compared with the primary prevention group (36.9 versus 15.7/1000 patient-years, P<0.001). In the total cohort, the primary end point was reduced with canagliflozin compared with placebo (26.9 versus 31.5/1000 patient-years; hazard ratio [HR], 0.86; 95% confidence interval [CI], 0.75-0.97; P<0.001 for noninferiority, P=0.02 for superiority) with no statistical evidence of heterogeneity (interaction P value=0.18) between the primary (HR, 0.98; 95% CI, 0.74-1.30) and secondary prevention (HR, 0.82; 95% CI, 0.72-0.95) cohorts. Renal outcomes (HR, 0.59; 95% CI, 0.44-0.79 versus HR, 0.63; 95% CI, 0.39-1.02; interaction P value=0.73) and heart failure hospitalization (HR, 0.68; 95% CI, 0.51-0.90 versus HR, 0.64; 95% CI, 0.35-1.15; interaction P value=0.91) were similarly reduced in the secondary and primary prevention cohorts, respectively. Lower extremity amputations were similarly increased in the secondary and primary prevention cohorts (HR, 2.07; 95% CI, 1.43-3.00 versus HR, 1.52; 95% CI, 0.70-3.29; interaction P value=0.63). CONCLUSIONS : Patients with type 2 diabetes mellitus and prior cardiovascular events had higher rates of cardiovascular outcomes compared with the primary prevention patients. Canagliflozin reduced cardiovascular and renal outcomes with no statistical evidence of heterogeneity of the treatment effect across the primary and secondary prevention groups. Additional studies will provide further insights into the effects of canagliflozin in these patient populations. CLINICAL TRIAL REGISTRATION : URL: https://www.clinicaltrials.gov. Unique identifiers: NCT01032629 and NCT01989754

Follow-up of blood-pressure lowering and glucose control in type 2 diabetes.

BACKGROUND In the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) factorial trial, the combination of perindopril and indapamide reduced mortality among patients with type 2 diabetes, but intensive glucose control, targeting a glycated hemoglobin level of less than 6.5%, did not. We now report results of the 6-year post-trial follow-up. METHODS We invited surviving participants, who had previously been assigned to perindopril–indapamide or placebo and to intensive or standard glucose control (with the glucose-control comparison extending for an additional 6 months), to participate in a post-trial follow-up evaluation. The primary end points were death from any cause and major macrovascular events. RESULTS The baseline characteristics were similar among the 11,140 patients who originally underwent randomization and the 8494 patients who participated in the post-trial follow-up for a median of 5.9 years (blood-pressure–lowering comparison) or 5.4 years (glucose-control comparison). Between-group differences in blood pressure and glycated hemoglobin levels during the trial were no longer evident by the first post-trial visit. The reductions in the risk of death from any cause and of death from cardiovascular causes that had been observed in the group receiving active blood-pressure–lowering treatment during the trial were attenuated but significant at the end of the post-trial follow-up; the hazard ratios were 0.91 (95% confidence interval [CI], 0.84 to 0.99; P=0.03) and 0.88 (95% CI, 0.77 to 0.99; P=0.04), respectively. No differences were observed during follow-up in the risk of death from any cause or major macrovascular events between the intensive-glucose-control group and the standard-glucose-control group; the hazard ratios were 1.00 (95% CI, 0.92 to 1.08) and 1.00 (95% CI, 0.92 to 1.08), respectively. CONCLUSIONS The benefits with respect to mortality that had been observed among patients originally assigned to blood-pressure–lowering therapy were attenuated but still evident at the end of follow-up. There was no evidence that intensive glucose control during the trial led to long-term benefits with respect to mortality or macrovascular events

Dynamics of a ferromagnetic domain wall: avalanches, depinning transition and the Barkhausen effect

We study the dynamics of a ferromagnetic domain wall driven by an external magnetic field through a disordered medium. The avalanche-like motion of the domain walls between pinned configurations produces a noise known as the Barkhausen effect. We discuss experimental results on soft ferromagnetic materials, with reference to the domain structure and the sample geometry, and report Barkhausen noise measurements on Fe$_{21}$Co$_{64}$B$_{15}$ amorphous alloy. We construct an equation of motion for a flexible domain wall, which displays a depinning transition as the field is increased. The long-range dipolar interactions are shown to set the upper critical dimension to $d_c=3$, which implies that mean-field exponents (with possible logarithmic correction) are expected to describe the Barkhausen effect. We introduce a mean-field infinite-range model and show that it is equivalent to a previously introduced single-degree-of-freedom model, known to reproduce several experimental results. We numerically simulate the equation in $d=3$, confirming the theoretical predictions. We compute the avalanche distributions as a function of the field driving rate and the intensity of the demagnetizing field. The scaling exponents change linearly with the driving rate, while the cutoff of the distribution is determined by the demagnetizing field, in remarkable agreement with experiments.Comment: 17 RevTeX pages, 19 embedded ps figures + 1 extra figure, submitted to Phys. Rev.

Rayleigh loops in the random-field Ising model on the Bethe lattice

We analyze the demagnetization properties of the random-field Ising model on the Bethe lattice focusing on the beahvior near the disorder induced phase transition. We derive an exact recursion relation for the magnetization and integrate it numerically. Our analysis shows that demagnetization is possible only in the continous high disorder phase, where at low field the loops are described by the Rayleigh law. In the low disorder phase, the saturation loop displays a discontinuity which is reflected by a non vanishing magnetization m_\infty after a series of nested loops. In this case, at low fields the loops are not symmetric and the Rayleigh law does not hold.Comment: 8pages, 6 figure

Long-term Benefits of Intensive Glucose Control for Preventing End-Stage Kidney Disease: ADVANCE-ON

OBJECTIVE The Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation (ADVANCE) trial reported that intensive glucose control prevents end-stage kidney disease (ESKD) in patients with type 2 diabetes, but uncertainty about the balance between risks and benefits exists. Here, we examine the long-term effects of intensive glucose control on risk of ESKD and other outcomes. RESEARCH DESIGN AND METHODS Survivors, previously randomized to intensive or standard glucose control, were invited to participate in post-trial follow-up. ESKD, defined as the need for dialysis or kidney transplantation, or death due to kidney disease, was documented overall and by baseline CKD stage, along with hypoglycemic episodes, major cardiovascular events, and death from other causes. RESULTS A total of 8,494 ADVANCE participants were followed for a median of 5.4 additional years. In-trial HbA1c differences disappeared by the first post-trial visit. The in-trial reductions in the risk of ESKD (7 vs. 20 events, hazard ratio [HR] 0.35, P = 0.02) persisted after 9.9 years of overall follow-up (29 vs. 53 events, HR 0.54, P 0.26). CONCLUSIONS Intensive glucose control was associated with a long-term reduction in ESKD, without evidence of any increased risk of cardiovascular events or death. These benefits were greater with preserved kidney function and with well-controlled blood pressure

Critical Hysteresis from Random Anisotropy

Critical hysteresis in ferromagnets is investigated through a $N$-component spin model with random anisotropies, more prevalent experimentally than the random fields used in most theoretical studies. Metastability, and the tensorial nature of anisotropy, dictate its physics. Generically, random field Ising criticality occurs, but other universality classes exist. In particular, proximity to $\mathcal{O}(N)$ criticality may explain the discrepancy between experiment and earlier theories. The uniaxial anisotropy constant, which can be controlled in magnetostrictive materials by an applied stress, emerges as a natural tuning parameter.Comment: four pages, revtex4; minor corrections in the text and typos corrected (published version

Crises and collective socio-economic phenomena: simple models and challenges

Financial and economic history is strewn with bubbles and crashes, booms and busts, crises and upheavals of all sorts. Understanding the origin of these events is arguably one of the most important problems in economic theory. In this paper, we review recent efforts to include heterogeneities and interactions in models of decision. We argue that the Random Field Ising model (RFIM) indeed provides a unifying framework to account for many collective socio-economic phenomena that lead to sudden ruptures and crises. We discuss different models that can capture potentially destabilising self-referential feedback loops, induced either by herding, i.e. reference to peers, or trending, i.e. reference to the past, and account for some of the phenomenology missing in the standard models. We discuss some empirically testable predictions of these models, for example robust signatures of RFIM-like herding effects, or the logarithmic decay of spatial correlations of voting patterns. One of the most striking result, inspired by statistical physics methods, is that Adam Smith's invisible hand can badly fail at solving simple coordination problems. We also insist on the issue of time-scales, that can be extremely long in some cases, and prevent socially optimal equilibria to be reached. As a theoretical challenge, the study of so-called "detailed-balance" violating decision rules is needed to decide whether conclusions based on current models (that all assume detailed-balance) are indeed robust and generic.Comment: Review paper accepted for a special issue of J Stat Phys; several minor improvements along reviewers' comment