Conduction in jammed systems of tetrahedra

Control of transport processes in composite microstructures is critical to the development of high performance functional materials for a variety of energy storage applications. The fundamental process of conduction and its control through the manipulation of granular composite attributes (e.g., grain shape) are the subject of this work. We show that athermally jammed packings of tetrahedra with ultra-short range order exhibit fundamentally different pathways for conduction than those in dense sphere packings. Highly resistive granular constrictions and few face-face contacts between grains result in short-range distortions from the mean temperature field. As a consequence, 'granular' or differential effective medium theory predicts the conductivity of this media within 10% at the jamming point; in contrast, strong enhancement of transport near interparticle contacts in packed-sphere composites results in conductivity divergence at the jamming onset. The results are expected to be particularly relevant to the development of nanomaterials, where nanoparticle building blocks can exhibit a variety of faceted shapes.Comment: 9 pages, 10 figure

Image based tracking approaches to AR/C at the Johnson Space Center

Automated Rendezvous and Capture (AR&C) requires the determination of the six degrees of freedom relating two free bodies. Sensor systems that can provide such information have varying sizes, weights, power requirements, complexities and accuracies. One type of sensor system which can provide several key advantages is an image based tracking system, or better known as a machine vision system. By image based tracking we mean that the sensor is some imaging device such as one or more video cameras, from which the tracking parameters necessary to support the rendezvous and capture operations (range, attitude, etc.) can be derived. Image based tracking offers many advantages such as relative hardware simplicity and reprogrammability. These advantages must be weighed against the disadvantages of these systems, such as limited operational range, poorer accuracy at greater distances and sensitivity to lighting conditions. However, with properly designed algorithms and targets these disadvantages can be minimized for many important applications. Rigorous testing in realistic environments can further increase the robustness and reliability of these systems. This presentation describes the facilities used at JSC to support AR&C image based tracking development and the details of our binocular stereo approach to image based tracking

The Creditors' Financial Reorganization Decision: New Evidence from Canadian Data

The paper examines a data set of 338 randomly selected financial reorganization plans filed in Canada during the period 1978-87. Creditors reject roughly 25% of reorganization plans, while about 20% of the plans creditors accept fail before completion, providing evidence of filtering failure in the reorganization process. A logit model of the creditors' reorganization decision produces two interesting results. Plans offering a high proportion of cash payments are more likely to be accepted by creditors, which we interpret as evidence that cash is a signal of financial viability. Plans with high ratios of secured debt are more likely to be accepted, which we interpret as evidence that secured creditors with insider knowledge signal information about the financial viability of firms to unsecured creditors. Ce document a pour but d'étudier le processus de réorganisation financière au Canada sur la base d'un échantillon de 338 propositions de réorganisations commerciales au cours de la période 1978-1987. Les données démontrent que 25 % des propositions sont rejetées par les créanciers non-garantis et qu'environ 20 % des propositions acceptées résultent éventuellement en un échec. Une analyse du comportement des créanciers lors du vote sur une proposition génère deux résultats intéressants. Premièrement, la probabilité d'acceptation d'une proposition augmente avec la proportion des paiements comptants fait aux créanciers. L'utilisation de paiements comptants est interprêtée comme un signal quand à la viabilité d'une firme. Deuxièmement, la probabilité d'acceptation d'une proposition augmente avec la proportion des créances garanties à l'intérieur de la firme. Ce résultat supporte la thèse à l'effet que les banques possèdent de l'information privilégiée sur la viabilité des entreprises et fournit une nouvelle évidence quant au rôle des banques dans la transmission de cette information vers les créanciers non-garantis.Financial reorganization; Creditors; Financial viability of firms, Réorganisation financière ; Créanciers ; Viabilité des entreprises

Should We Abolish Chapter 11 : Evidence from Canada

Over the last decade, Chapter 11 has been the brunt of serious criticism. Some American jurists arguing in favor of revising Chapter 11 have raised the possibility that the Canadian reorganization system might be a good alternative to the existing U.S. system. This article argues that there are fruitful lessons to be learned from the Canadian experience with court-supervised reorganization. Canadian evidence shows that acceptance, confirmation, and consummation rates of proposals are very high. Moreover, firms reorganizing in Canada are almost ten times more likely to survive reorganization than their American counterparts. Furthermore, Canadian data yield no support for the claim that problems with bankruptcy law result from an over-abundance of small firms in reorganization. The analysis also shows that the Canadian reorganization procedure offers a very rapid solution to financial distress and that creditors gain, in expected value terms, from reorganization over liquidation. Based on our evaluation of the relative performance of both systems, we argue that Chapter 11 be revised rather than repealed. Au cours de la dernière décennie, le Chapitre 11 du U.S. Bankruptcy Code a été l'objet de critiques importantes de la part de juristes et d'économistes américains. Récemment, un certain nombre de ces juristes ont soulevé la possibilité de réformer le Chapitre 11 sur la base du système canadien en matière de réorganisation commerciale. Le but du présent article est de démontrer que l'expérience canadienne en matière de réorganisation commerciale est révélatrice sur les réformes potentielles à apporter au Chapitre 11. Les données canadiennes montrent clairement que les taux d'acceptation, de confirmation et de succès des propositions commerciales sont très élevés. De plus, la probabilité de survie des firmes canadiennes en réorganisation est de dix fois supérieure à celle des firmes américaines. Les données canadiennes permettent également de rejeter l'affirmation selon laquelle l'échec de la procédure de réorganisation origine de son utilisation par les petites entreprises. Qui plus est, la procédure canadienne offre une solution rapide aux entreprises en difficultés financières et un rendement espéré aux créanciers supérieur par rapport à la procédure de liquidation. Sur la base de notre évaluation comparative des deux systèmes d'insolvabilité, nous suggérons la révision plutôt que l'abolition du Chapitre 11.Bankruptcy, Reorganization, Chapter 11, Bankruptcy Act, Faillite, Réorganisation, Chapitre 11, Loi sur la faillite

A binocular stereo approach to AR/C at the Johnson Space Center

Automated Rendezvous and Capture requires the determination of the 6 DOF relating two free bodies. Sensor systems that can provide such information have varying sizes, weights, power requirements, complexities, and accuracies. One type of sensor system that can provide several key advantages is a binocular stereo vision system

HIV-1 reverse transcriptase mutations that confer decreased in vitro susceptibility to anti-RT DNA aptamer RT1t49 confer cross resistance to other anti-RT aptamers but not to standard RT inhibitors

RNA and DNA aptamers specific for HIV-1 reverse transcriptase (RT) can inhibit reverse transcription in vitro. RNA aptamers have been shown to potently block HIV-1 replication in culture. We previously reported mutants of HIV-1 RT with substitutions N255D or N265D that display resistance to the DNA aptamer RT1t49. Variant viruses bearing these mutations singly or in combination were compromised for replication. In order to address the wider applicability of such aptamers, HIV-1 RT variants containing the N255D, N265D or both (Dbl) were tested for the extent of their cross-resistance to other DNA/RNA aptamers as well as to other RT inhibitors. Both N265D and Dbl RTs were resistant to most aptamers tested. N255D mutant displayed mild resistance to two of the DNA aptamers, little change in sensitivity to three and hypersensitivity to one. Although all mutants displayed wild type-like ribonuclease H activity, their activity was compromised under conditions that prevent re-binding. This suggests that the processivity defect caused by these mutations can also affect RNase H function thus contributing further to the replication defect in mutant viruses. These results indicate that mutants conferring resistance to anti-RT aptamers significantly affect many HIV-1 RT enzymatic activities, which could contribute to preventing the development of resistance in vivo. If such mutations were to arise in vivo, our results suggest that variant viruses should remain susceptible to many existing anti-RT inhibitors. This result was tempered by the observation that NRTI-resistance mutations such as K65R can confer resistance to some anti-RT aptamers

In Memoriam, Phillip Blumberg’s Legacy: A Dean’s Perspective

Phillip I. Blumberg served as Dean of the University of Connecticut School of Law from 1974 to 1984. These remarks were first delivered at the University of Connecticut School of Law’s tribute to Dean Blumberg, “Honoring Phillip I. Blumberg,” held on December 10, 2021. They have been lightly edited for publication