Developing limits for driving under cannabis

ABSTRACT Objective Development of a rational and enforceable basis for controlling the impact of cannabis use on traffic safety. Methods An international working group of experts on issues related to drug use and traffic safety evaluated evidence from experimental and epidemiological research and discussed potential approaches to developing per se limits for cannabis. Results In analogy to alcohol, finite (non-zero) per se limits for delta-9-tetrahydrocannabinol (THC) in blood appear to be the most effective approach to separating drivers who are impaired by cannabis use from those who are no longer under the influence. Limited epidemiological studies indicate that serum concentrations of THC below 10 ng/ml are not associated with an elevated accident risk. A comparison of meta-analyses of experimental studies on the impairment of driving-relevant skills by alcohol or cannabis suggests that a THC concentration in the serum of 7-10 ng/ml is correlated with an impairment comparable to that caused by a blood alcohol concentration (BAC) of 0.05%. Thus, a suitable numerical limit for THC in serum may fall in that range. Conclusions This analysis offers an empirical basis for a per se limit for THC that allows identification of drivers impaired by cannabis. The limited epidemiological data render this limit preliminary

Reactive nanometer multilayers as tailored heat sources for joining techniques

Established joining techniques like welding, soldering or brazing typically are characterized by a large amount of heat input into the components. Especially in the case of heat sensitive structures like MEMS this often results in stress induced deformation and degradation or even in damaging the parts. Therefore, there is an urgent need for a more reliable and reproducible method for joining, which is characterized by a well defined and small heat input for only a short time period. So-called reactive nanometer multilayers offer a promising approach to meet these needs. Reactive nanometer multilayers consist of several hundreds or thousands of alternating nanoscale layers, which can react with each other. Placing a reactive nanometer multilayer between two surfaces already applied with a solder or brazing metal, it can be used as a controllable local heat source. After activating the chemical reaction by an electrical spark, laser pulse or impact, a self-sustaining intermixing reaction starts, which travels the length of the reactive nanometer multilayer resulting in a stable intermetallic material, such as NiAl. The peak temperature of the reaction can be well above 1000 deg C, but it only reaches this temperature for milliseconds, so that the heat is localized to the solder layers. The component remains at room temperature during the entire process. We will present first results in the fabrication of reactive nanometer multilayers by magnetron and ion beam sputter deposition, the fabrication of free standing nanometer multilayers and first joining experiments. Furthermore, we will give an outlook on future developments, such as alternative material combinations for the generation of higher or lower amounts of hea

Reactive nanometer mulitlayers as tailored heat sources for joining techniques

Established joining techniques like welding, soldering or brazing typically are characterized by a large amount of heat input into the components. Especially in the case of heat sensitive structures like MEMS this often results in stress induced deformation and degradation or even in damaging the parts. Therefore, there is an urgent need for a more reliable and reproducible method for joining, which is characterized by a well defined and small heat input for only a short time period. So-called reactive nanometer multilayers offer a promising approach to meet these needs. Reactive nanometer multilayers consist of several hundreds or thousands of alternating nanoscale layers, which can exothermicly react with each other. Placing a reactive nanometer multilayer coated with a solder or brazing layer between two surfaces, it can be used as a controllable local heat source for joining. After activating the chemical reaction by an electrical spark, laser pulse or mechanical impact, aself-sustaining intermixing reaction starts, which propagates through the whole film resulting in a stable intermetallic compound, such as NiAl. The peak temperature of the reaction can be well above 1400 °C, but this temperature is only reached for milliseconds, so that the heat is localized to the solder layers. The components itself remain at room temperature during the entire process

Ptychography with multilayer Laue lenses

Two different multilayer Laue lens designs were made with total deposition thicknesses of 48 mu m and 53 mu m, and focal lengths of 20.0 mm and 12.5 mm at 20.0 keV, respectively. From these two multilayer systems, several lenses were manufactured for one-and two-dimensional focusing. The latter is realised with a directly bonded assembly of two crossed lenses, that reduces the distance between the lenses in the beam direction to 30 mm and eliminates the necessity of producing different multilayer systems. Characterization of lens fabrication was performed using a laboratory X-ray microscope. Focusing properties have been investigated using ptychography

Full-field X-ray microscopy with crossed partial multilayer Laue lenses

We demonstrate full-field X-ray microscopy using crossed multilayer Laue lenses (MLL). Two partial MLLs are prepared out of a 48 μm high multilayer stack consisting of 2451 alternating zones of WSi2 and Si. They are assembled perpendicularly in series to obtain two-dimensional imaging. Experiments are done in a laboratory X-ray microscope using Cu-Kα radiation (E = 8.05 keV, focal length f = 8.0 mm). Sub-100 nm resolution is demonstrated without mixed-order imaging at an appropriate position of the image plane. Although existing deviations from design parameters still cause aberrations, MLLs are a promising approach to realize hard X-ray microscopy at high efficiencies with resolutions down to the sub-10 nm range in future