KPZ in one dimensional random geometry of multiplicative cascades

We prove a formula relating the Hausdorff dimension of a subset of the unit interval and the Hausdorff dimension of the same set with respect to a random path matric on the interval, which is generated using a multiplicative cascade. When the random variables generating the cascade are exponentials of Gaussians, the well known KPZ formula of Knizhnik, Polyakov and Zamolodchikov from quantum gravity appears. This note was inspired by the recent work of Duplantier and Sheffield proving a somewhat different version of the KPZ formula for Liouville gravity. In contrast with the Liouville gravity setting, the one dimensional multiplicative cascade framework facilitates the determination of the Hausdorff dimension, rather than some expected box count dimension.Comment: 14 page

2-[Bis(2-amino­ethyl)amino]ethanaminium chloride dichloro­methane solvate

In the title compound, C6H19N4 +·Cl−·CH2Cl2, the non-H atoms of the ammonium ion show non-crystallographic C 3 symmetry. The chloride ion is embedded in a framework of seven crystallographically independent hydrogen bonds (five N—H⋯Cl and two C—H⋯Cl), which form layers parallel to the (100) plane. Two N---H...N bonds also occur

Crash incompatibility: Cars versus light trucks and vans

Background: In crashes between a car and a light truck or van (LTV), car occupants are more likely to be killed than LTV occupants. The extent to which this is due to the greater harm imposed by LTVs on cars or to the greater protection they offer their own occupants is not known. The combined effect of these two factors is also unknown. Objective: To estimate the harm imposed and protection offered by LTVs compared to cars, the joint effect of these on the risk of crash death, and the effects of two LTV design features: bumper height and frame type (unibody versus body-on-frame). Methods: Case-control analyses of two-vehicle collisions involving passenger vehicles in the United States. Findings: Adjusted for the type of vehicle they were riding in and for other confounders, occupants of any vehicle that collided with LTVs were at higher risk of death compared with occupants who collided with a car. For the six types of LTV, the adjusted odds ratios (aOR) ranged from 1.8 (95% confidence interval 1.5 to 2.1) for collision with a compact pickup to 4.8 (3.9 to 5.8) for collision with a full-size van. Occupants of LTVs were at lower risk of death compared with car occupants. For the six types of LTV, the aOR ranged from 0.32 (0.25 to 0.41) for occupants of full-size pickups to 0.76 (0.66 to 0.87) for occupants of compact SUVs. Compared to crashes between two cars, the joint relative risk of death in crashes between any other combination of two vehicle types ranged from 1.0 to 2.6, suggesting that occupants in crashes between two cars have the lowest risk of death. SUVs and pickups with bumpers that matched car bumpers in height posed lower risk to car occupants in side crashes (aOR 0.72 (0.54 to 0.95)), but there was little evidence of a beneficial effect in head-on crashes (a0R 1.20 (0.65 to 2.21)). Unibody SUVs posed less risk to occupants of other vehicles than did body-on-frame SUVs (aOR, 0.83 (0.73 to 0.94)), while also protecting their own occupants better (aOR 0.85 (0.70 to 1.03)). Conclusion: Although LTVs protect their own occupants better than cars do, LTVs are associated with an excess total risk of death in crashes with cars or other LTVs

Freeway speed limits and traffic fatalities in washington state.

Abstract Background: In 1987 individual states in the USA were allowed to raise speed limits on rural freeways from 55 to 65 mph. Analyses of the impact of the increased speed limits on highway safety have produced conflicting results. Objecti6e: To determine if the 1987 speed limit increase on Washington State's rural freeways affected the incidence of fatal crashes or all crashes on rural freeways, or affected average vehicle speeds or speed variance. Design: An ecological study of crashes and vehicle speeds on Washington State freeways from 1974 through 1994. Results: The incidence of fatal crashes more than doubled after 1987, compared with what would have been expected if there had been no speed limit increase, rate ratio 2.1 (95% confidence interval (CI), 1.6-2.7). This resulted in an excess of 26.4 deaths per year on rural freeways in Washington State. The total crash rate did not change substantially, rate ratio 1.1 (95% CI, 1.0-1.3). Average vehicle speed increased by 5.5 mph. Speed variance was not affected by the speed limit increase. Conclusions: The speed limit increase was associated with a higher fatal crash rate and more deaths on freeways in Washington State

Influence of thermal post-curing on the degradation of a cross-linked polybenzimidazole-based membrane for high temperature polymer electrolyte membrane fuel cells

The lifetime stability of membranes is one of the main requirements regarding reliability of high temperature polymer electrolyte membrane fuel cells. The present work has improved durability under cycled operation by thermal post-curing of cross-linked polybenzimidazole (PBI)-based membranes. The membranes were dried over 1, 2 and 3 h at 250 degrees C under air. Ex-situ experiments proved an increase in stability by post-curing. The liquid uptake and swelling in phosphoric acid increased with longer curing periods. The effect of thermal treatments on cycle stability, lifetime and begin-of-life performance of the membrane electrode assemblies (MEAs) was investigated. Longer post-curing periods of the membranes had no influence on the MEAs' begin-of-life performance and constant current behavior over 2300 h. However, the 3 h post-cured MEAs showed enhanced cycle stability. Post-mortem analysis was carried out to identify the occurring degradation mechanisms. While a significant loss of phosphoric acid and a reduction of electrochemical surface activity on the cathode were observed for both post-cured MEAs, the 3 h dried membrane sample had a significantly higher resistance against pinhole formation during the long term test. Altogether, this work presents thermal post-curing as a promising method for the reduction of degradation determining effects in fuel cell membranes. (C) 2014 Elsevier B.V. All rights reserved