Neutron width statistics using a realistic description of the neutron channel

A basic prediction of the statistical model of compound nucleus reactions is that the partial widths for decay into any open channel channel fluctuate according to the Porter-Thomas distribution (PTD). A recent experiment on $s$- and $p$-wave neutron scattering from platinum isotopes found that the experimental $s$-wave partial neutron width distributions deviated substantially from the PTD. Several explanations for this finding have been proposed within the statistical model, but none has resolved this issue. Here, we review the application of a realistic resonance-reaction model to $s$-wave neutron scattering from $^{194}$Pt. Our main conclusion is that the PTD provides an excellent description of the partial neutron width distribution, provided that the secular energy dependence of the average neutron width is correctly described. Within a realistic range of model parameters, there can be a near-threshold bound or virtual state of the neutron channel that changes this secular dependence from the usual $\sqrt{E}$ dependence, as proposed by Weidenm\"uller [1]. In this case, the use of the $\sqrt{E}$ dependence to analyze the data will lead to apparent deviations from the PTD. We discuss the limited parameter range where such a near threshold state can have a significant effect.Comment: Proceedings of the 15th Varenna Conference on Nuclear Reaction Mechanisms. 7 pages, 4 figures, 1 tabl

Looking Forward: Professor Roberta Karmel\u27s Prescient Views on the Transformation of Self-Regulatory Organizations and of the Securities Market Structure at the Turn of the Last Century

This essay examines Professor Roberta Karmel’s scholarship on the transformation of self-regulatory organizations (SROs) and the securities market structure, a transformation that occurred at the turn of the last century. It explains how she examined the events from the perspective of a lawyer who had a rich knowledge of the history of the SROs, the securities markets, and their regulation and how she provided a practical understanding of the way these markets worked. It points out that, rather than offering an overarching theory that would explain all of these developments and that would guide regulators and legislators in SRO and securities market structure reforms, she pointed out problems and contradictions in the developments that, in her view, would have to be faced and addressed by both Congress and the SEC. The essay first sets out briefly the background to and a timeline for the SRO and securities market transformation and describes how that transformation closely intersects with Roberta’s career as a legal practitioner, a regulator, and a legal academic. It then looks at her scholarly discussion on how the self-regulatory functions of the stock exchanges became the Financial Industry Regulatory Authority (FINRA), where she raised the important question whether self-regulation by broker-dealers continued to exist post-FINRA. The essay explores a possible answer to this question, which Roberta has acknowledged, in a new form of self-regulation—the collaboration between FINRA and those officers in broker-dealers who are responsible for ensuring that they and their employees follow law and regulation, the compliance officers. It next looks at Roberta’s insights on the related subject of the transformation of the stock exchanges and its overall effects upon securities market structure, explaining how she identified for the legal academic audience the forces, including the regulatory ones, that were pushing the exchanges to become public companies and the market fragmentation that resulted from the proliferation of trading venues. It then explains that Roberta took a “wait and see” approach to problems in securities market structure, recommending that securities markets be allowed to develop with their new forms and technology before Congress and the SEC apply to them a major new regulatory framework and that the SEC regulate with a light hand, correcting market problems where necessary, while the outline of a new market structure emerged. The essay concludes by briefly looking at the current securities market from Roberta’s perspective

Epg5 links proteotoxic stress due to defective autophagic clearance and epileptogenesis in Drosophila and vici syndrome patients

Epilepsy is a common neurological condition that arises from dysfunctional neuronal circuit control due to either acquired or innate disorders. Autophagy is an essential neuronal housekeeping mechanism, which causes severe proteotoxic stress when impaired. Autophagy impairment has been associated to epileptogenesis through a variety of molecular mechanisms. Vici Syndrome (VS) is the paradigmatic congenital autophagy disorder in humans due to recessive variants in the ectopic P-granules autophagy tethering factor 5 (EPG5) gene that is crucial for autophagosome-lysosome fusion and autophagic clearance. Here, we used Drosophila melanogaster to study the importance of Epg5 in development, aging, and seizures. Our data indicate that proteotoxic stress due to impaired autophagic clearance and seizure-like behaviors correlate and are commonly regulated, suggesting that seizures occur as a direct consequence of proteotoxic stress and age-dependent neurodegenerative progression. We provide complementary evidence from EPG5-mutated patients demonstrating an epilepsy phenotype consistent with Drosophila predictions. Abbreviations: AD: Alzheimer's disease; ALS-FTD: Amyotrophic Lateral Sclerosis-FrontoTemoporal Dementia; DART: Drosophila Arousal Tracking; ECoG: electrocorticogram; EEG: electroencephalogram; EPG5: ectopic P-granules 5 autophagy tethering factor; KA: kainic acid; MBs: mushroom bodies; MRI magnetic resonance imaging; MTOR: mechanistic target of rapamycin kinase; PD: Parkinson's disease; TSC: TSC complex; VS: Vici syndrome.</p