Total Variation Blind Deconvolution: The Devil Is in the Details

In this paper we study the problem of blind deconvolution. Our analysis is based on the algorithm of Chan and Wong [2] which popularized the use of sparse gradient priors via total variation. We use this algorithm because many methods in the literature are essentially adaptations of this framework. Such algorithm is an iterative alternating energy minimization where at each step either the sharp image or the blur function are reconstructed. Recent work of Levin et al. [14] showed that any algorithm that tries to minimize that same energy would fail, as the desired solution has a higher energy than the no-blur solution, where the sharp image is the blurry input and the blur is a Dirac delta. However, experimentally one can observe that Chan and Wong's algorithm converges to the desired solution even when initialized with the no-blur one. We provide both analysis and experiments to resolve this paradoxical conundrum. We find that both claims are right. The key to understanding how this is possible lies in the details of Chan and Wong's implementation and in how seemingly harmless choices result in dramatic effects. Our analysis reveals that the delayed scaling (normalization) in the iterative step of the blur kernel is fundamental to the convergence of the algorithm. This then results in a procedure that eludes the no-blur solution, despite it being a global minimum of the original energy. We introduce an adaptation of this algorithm and show that, in spite of its extreme simplicity, it is very robust and achieves a performance comparable to the state of the art.

Light stops, blind spots, and isospin violation in the MSSM

In the framework of the MSSM, we examine several simplified models where only a few superpartners are light. This allows us to study WIMP-nucleus scattering in terms of a handful of MSSM parameters and thereby scrutinize their impact on dark matter direct-detection experiments. Focusing on spin-independent WIMP-nucleon scattering, we derive simplified, analytic expressions for the Wilson coefficients associated with Higgs and squark exchange. We utilize these results to study the complementarity of constraints due to direct-detection, flavor, and collider experiments. We also identify parameter configurations that produce (almost) vanishing cross sections. In the proximity of these so-called blind spots, we find that the amount of isospin violation may be much larger than typically expected in the MSSM. This feature is a generic property of parameter regions where cross sections are suppressed, and highlights the importance of a careful analysis of the nucleon matrix elements and the associated hadronic uncertainties. This becomes especially relevant once the increased sensitivity of future direct-detection experiments corners the MSSM into these regions of parameter space.

First generation versus second generation drug-eluting stents for the treatment of bifurcations: 5-year follow-up of the LEADERS all-comers randomized trial.

BACKGROUND Historically, percutaneous coronary intervention (PCI) of bifurcation lesions was associated with worse procedural and clinical outcomes when compared with PCI of non-bifurcation lesions. Newer generation drug-eluting stents (DES) might improve long-term clinical outcomes after bifurcation PCI. METHODS AND RESULTS The LEADERS trial was a 10-center, assessor-blind, non-inferiority, all-comers trial, randomizing 1,707 patients to treatment with a biolimus A9(TM) -eluting stent (BES) with an abluminal biodegradable polymer or a sirolimus-eluting stent (SES) with a durable polymer (ClinicalTrials.gov Identifier: NCT00389220). Five-year clinical outcomes were compared between patients with and without bifurcation lesions and between BES and SES in the bifurcation lesion subgroup. There were 497 (29%) patients with at least 1 bifurcation lesion (BES = 258; SES = 239). At 5-year follow-up, the composite endpoint of cardiac death, myocardial infarction (MI) and clinically-indicated (CI) target vessel revascularization (TVR) was observed more frequently in the bifurcation group (26.6% vs. 22.4%, P = 0.049). Within the bifurcation lesion subgroup, no differences were observed in (cardiac) death or MI rates between BES and SES. However, CI target lesion revascularization (TLR) (10.1% vs. 15.9%, P = 0.0495), and CI TVR (12.0% vs. 19.2%, P = 0.023) rates were significantly lower in the BES group. Definite/probable stent thrombosis (ST) rate was numerically lower in the BES group (3.1% vs. 5.9%, P = 0.15). Very late (>1 year) definite/probable ST rates trended to be lower with BES (0.4% vs. 3.1%, P = 0.057). CONCLUSIONS In the treatment of bifurcation lesions, use of BES led to superior long-term efficacy compared with SES. Safety outcomes were comparable between BES and SES, with an observed trend toward a lower rate of very late definite/probable ST between 1 and 5 years with the BES. © 2015 Wiley Periodicals, Inc.

A double-blind randomised study to evaluate the efficacy and safety of bindarit in preventing coronary stent restenosis.

AIMS Bindarit (BND) is a selective inhibitor of monocyte chemotactic protein-1 (MCP-1/CCL2), which plays an important role in generating intimal hyperplasia. Our aim was to explore the efficacy and safety of bindarit in preventing restenosis following percutaneous coronary intervention. METHODS AND RESULTS A phase II, double-blind, multicentre randomised trial included 148 patients randomised into three arms (BND 600 mg, n=48; BND 1,200 mg, n=49; PLB, n=51). Bindarit was given following PCI and continued for 180 days. Monthly clinical follow-up and six-month coronary angiography were conducted. The primary endpoint was in-segment late loss; the main secondary endpoints were in-stent late loss and major adverse cardiovascular events. Efficacy analysis was carried out on two populations, ITT and PP. There were no significant differences in the baseline characteristics among the three treatment groups. In-segment and in-stent late loss at six months in BND 600, BND 1,200 and PLB were: (ITT 0.54 vs. 0.52 vs. 0.72; p=0.21), (PP 0.46 vs. 0.53 vs. 0.72; p=0.12) and (ITT 0.74 vs. 0.74 vs. 1.05; p=0.01), (PP 0.66 vs. 0.73 vs. 1.06; p=0.003), respectively. The MACE rates at nine months among treatment groups were 20.8% vs. 28.6% vs. 25.5% (p=0.54), respectively. CONCLUSIONS This was a negative study with the primary endpoint not being met. However, significant reduction in the in-stent late loss suggests that bindarit probably exerts a favourable action on the vessel wall following angioplasty. Bindarit was well tolerated with a compliance rate of over 90%. A larger study utilising a loading dose and targeting a specific patient cohort may demonstrate more significant results.