Optical Subcarrier Communications

This paper discusses the use of rf subcarriers placed on optical beams for communication purposes. Through the use of advanced optical beam processing and post detection electronic processing, the advantages of optical frequency techniques can be combined with the mature background of the rf technology. These techniques are expected to find applications for long range wideband communication, spacecraft tracking and rendezvous, and altimetry, as well as for aircraft and spacecraft landing aids

The Circumcision Issue

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68100/2/10.1177_000992289903800407.pd

Relating geologic units and mobility system kinematics contributing to Curiosity wheel damage at Gale Crater, Mars

Curiosity landed on plains to the north of Mount Sharp in August 2012. By June 2016 the rover had traversed 12.9 km to the southwest, encountering extensive strata that were deposited in a fluvial-deltaic-lacustrine system. Initial drives across sharp sandstone outcrops initiated an unacceptably high rate of punctures and cracks in the thin aluminum wheel skin structures. Initial damage was found to be related to the drive control mode of the six wheel drive actuators and the kinematics of the rocker-bogie suspension. Wheels leading a suspension pivot were forced onto sharp, immobile surfaces by the other wheels as they maintained their commanded angular velocities. Wheel damage mechanisms such as geometry-induced stress concentration cracking and low-cycle fatigue were then exacerbated. A geomorphic map was generated to assist in planning traverses that would minimize further wheel damage. A steady increase in punctures and cracks between landing and June 2016 was due in part because of drives across the sharp sandstone outcrops that could not be avoided. Wheel lifetime estimates show that with careful path planning the wheels will be operational for an additional ten kilometers or more, allowing the rover to reach key strata exposed on the slopes of Mount Sharp

Characteristics of pebble and cobble-sized clasts along the Curiosity rover traverse from sol 100 to 750: Terrain types, potential sources, and transport mechanisms

We combine the results of orbitally-derived morphologic and thermal inertia data with in situ observations of abundance, size, morphologic characteristics, and distribution of pebble- to cobble-sized clasts along the Curiosity rover traverse. Our goals are to characterize rock sources and transport history, and improve our ability to predict upcoming terrain. There are ten clast types, with nine types interpreted as sedimentary rocks. Only Type 3 clasts had morphologies indicative of significant wear through transport; thus, most clast types are indicative of nearby outcrops or prior presence of laterally extensive sedimentary rock layers, consistent with the erosional landscape. A minor component may reflect impact delivery of more distant material. Types 1 and 4 are heavily-cemented sandstones, likely associated with a “caprock” layer. Types 5 and 6 (and possibly 7) are pebble-rich sandstones, with varying amounts of cement leading to varying susceptibility to erosion/wear. Type 3 clasts are rounded pebbles likely transported and deposited alluvially, then worn out of pebbly sandstone/conglomerate. Types 9 and 10 are poorly-sorted sandstones, with Type 9 representing fragments of Square Top-type layers, and Type 10 deriving from basal or other Mt. Sharp layers. Types 2, 8 and 9 are considered exotics. There are few clear links between clast type and terrain surface roughness (particularly in identifying terrain that is challenging for the rover to navigate). Orbital data may provide a reasonable prediction of certain end-member terrains but the complex interplay between variables that contribute to surface characteristics makes discriminating between terrain types from orbital data problematic. Prediction would likely be improved through higher-resolution thermal inertia data

The short-term impact of 3 smoked cannabis preparations versus placebo on PTSD symptoms: A randomized cross-over clinical trial.

ImportanceThere is a pressing need for development of novel pharmacology for the treatment of Posttraumatic Stress Disorder (PTSD). Given increasing use of medical cannabis among US military veterans to self-treat PTSD, there is strong public interest in whether cannabis may be a safe and effective treatment for PTSD.ObjectiveThe aim of the present study was to collect preliminary data on the safety and potential efficacy of three active concentrations of smoked cannabis (i.e., High THC = approximately 12% THC and MethodsThe study used a double-blind, cross-over design, where participants were randomly assigned to receive three weeks of either active treatment or placebo in Stage 1 (N = 80), and then were re-randomized after a 2-week washout period to receive one of the other three active treatments in Stage 2 (N = 74). The primary outcome measure was change in PTSD symptom severity from baseline to end of treatment in Stage 1.ResultsThe study did not find a significant difference in change in PTSD symptom severity between the active cannabis concentrations and placebo by the end of Stage 1. All three active concentrations of smoked cannabis were generally well tolerated.Conclusions and relevanceThe present study is the first randomized placebo-controlled trial of smoked cannabis for PTSD. All treatment groups, including placebo, showed good tolerability and significant improvements in PTSD symptoms during three weeks of treatment, but no active treatment statistically outperformed placebo in this brief, preliminary trial. Additional well-controlled and adequately powered studies with cannabis suitable for FDA drug development are needed to determine whether smoked cannabis improves symptoms of PTSD.Trial registrationIdentifier: NCT02759185; ClinicalTrials.gov