UAS for Public Safety: Active Threat Recognition

The Center for Homeland Defense and Security identified an increase of active threat events, such as mass shootings, annually since 1999. Literature suggests that 90% of shootings were over before law enforcement arrived at the scene and the first responder response was limited to “surround and contain” until Special Weapons and Tactics Teams (SWAT) arrived on the scene. Using Unmanned Aircraft Systems (UAS) to detect which individual was the threat and type of weapon used can provide useful information to increase the speed of the response for first-on-scene rather than waiting for SWAT if the type of weapon was known. A UAS equipped with a full spectrum sensor compared traditional red-green-blue (RGB) images to near-infrared (NIR) images in a simulated active threat scenario. A true positive rate (TPR) metric was used to measure the percentage of correctly-detected weapons consisting of either a knife, pistol, rifle, shotgun, or shovel at slant range distances of 25-, 50-, 75-, and 100-feet respectively. A convenience sample of 102 survey participants, recruited from constituents of the Airborne Public Safety Association (APSA) and DRONERESPONDERS was conducted to observe 48 randomly-presented images to determine which type of weapon was detected. The results suggest that survey participants could correctly detect weapons at a 12% greater rate with the NIR sensor than the RGB sensor; however, the pistol had the largest difference in TPR between NIR and RGB sensors. The pistol had an increased probability of detection by 33% when using the NIR sensor compared to an RGB sensor. Additionally, differences were also observed between slant range distances. The closest distance of 25 feet showed a 42% increase in participants’ ability to correctly determine the weapon type compared to the 100-foot slant range distance. Therefore, using a NIR sensor-equipped UAS at flying a maximum slant range distance of 50 feet may help a first-responder determine the type of weapon before SWAT arrives on the scene

Infrared ellipsometry study of photogenerated charge carriers at the (001) and (110) surfaces of SrTiO3 crystals and at the interface of the corresponding LaAlO3/SrTiO3 heterostructures

2-DIMENSIONAL ELECTRON-GAS; STRONTIUM-TITANATE; PERSISTENT PHOTOCONDUCTIVITY; DOMAIN-STRUCTURE; MOBILITY; TEMPERATURE; TRANSITION; FILMS; GAMMA-AL2O3/SRTIO3; FERROELECTRICITYThe work at the University of Fribourg was supported by the Schweizerische Nationalfonds (SNF) through Grant No. 200020-153660. B.P.P.M. wishes to acknowledge support from the Marsden Fund of New Zealand. The work at MUNI was financially supported by the Ministry of education youth and sports of the Czech Republic, under the project CEITEC 2020 (LQ1601). M.S., F.S., and G.H. acknowledge the support by the Spanish Government through Project No. MAT2014-56063-C2-1-R, the Severo Ochoa Grant No. SEV-2015-0496, and the Generalitat de Catalunya (Project No. 2014SGR 734). J. Mannhart is acknowledged for providing the LAO/STO (001) sample and J. Foncuberta for scientific discussion.Peer reviewe

Infrared ellipsometry study of photogenerated charge carriers at the (001) and (110) surfaces of SrTiO3\mathrm{SrTi}{\mathrm{O}}_{3} crystals and at the interface of the corresponding LaAlO3/SrTiO3\mathrm{LaAl}{\mathrm{O}}_{3}/\mathrm{SrTi}{\mathrm{O}}_{3} heterostructures

With infrared (IR) ellipsometry and dc resistance measurements, we investigated the photodoping at the (001) and (110) surfaces of SrTiO3 (STO) single crystals and at the corresponding interfaces of LaAlO3/SrTiO3 (LAO/STO) heterostructures. In the bare STO crystals, we find that the photogenerated charge carriers, which accumulate near the (001) surface, have a similar depth profile and sheet carrier concentration as the confined electrons that were previously observed in LAO/STO (001) heterostructures. A large fraction of these photogenerated charge carriers persist at low temperature at the STO (001) surface even after the ultraviolet light has been switched off again. These persistent charge carriers seem to originate from oxygen vacancies that are trapped at the structural domain boundaries, which develop below the so-called antiferrodistortive transition at T∗=105K. This is most evident from a corresponding photodoping study of the dc transport in STO (110) crystals for which the concentration of these domain boundaries can be modified by applying a weak uniaxial stress. The oxygen vacancies and their trapping by defects are also the source of the electrons that are confined to the interface of LAO/STO (110) heterostructures, which likely do not have a polar discontinuity as in LAO/STO (001). In the former, the trapping and clustering of the oxygen vacancies also has a strong influence on the anisotropy of the charge carrier mobility. We show that this anisotropy can be readily varied and even inverted by various means, such as a gentle thermal treatment, UV irradiation, or even a weak uniaxial stress. Our experiments suggest that extended defects, which develop over long time periods (of weeks to months), can strongly influence the response of the confined charge carriers at the LAO/STO (110) interface

Fretting corrosion of hafnium in simulated body fluids.

Hafnium has been suggested as an interesting material for biomedical applications due to its good biocompatibility and osteogenesis. However, its behaviour under fretting corrosion conditions, found in applications such as dental and joint implants, has not been studied in depth. A three-electrode electrochemical cell integrated with a ball-on-flat reciprocating tribometer was used to investigate the corrosion of hafnium and commercially pure (CP) titanium in simulated body fluids. An increased susceptibility to pitting corrosion was observed when hafnium was subjected to fretting. Open circuit potential measurements showed a more severe mechanical depassivation due to fretting in the case of CP titanium in comparison to hafnium. In addition, the anodic currents measured during potentiostatic tests were also higher for CP titanium

Collective nature of plasticity in mediating phase transformation under shock compression

An open question in the behavior of metals subjected to shock is the nature of the deformation that couples to the phase transformation process. Experiments to date cannot discriminate between the role of known deformation processes such as twinning or dislocations accompanying a phase change, and modes that can become active only in extreme environments. We show that a deformation mode not present in static conditions plays a dominant role in mediating plastic behavior in hcp metals and determines the course of the transformation. Our molecular dynamics simulations for titanium demonstrate that the transformation is preceded by a 90° lattice reorientation of the parent, and the growth of the reoriented domains is accompanied by the collective action of dislocations and deformation twins. We suggest how diffraction and transmission electron microscopy experiments may validate our findings.United States. Dept. of Energy (Contract DE-AC52-06NA25396

Pitfalls in the measurement of muscle mass: a need for a reference standard

Background All proposed definitions of sarcopenia include the measurement of muscle mass, but the techniques and threshold values used vary. Indeed, the literature does not establish consensus on the best technique for measuring lean body mass. Thus, the objective measurement of sarcopenia is hampered by limitations intrinsic to assessment tools. The aim of this study was to review the methods to assess muscle mass and to reach consensus on the development of a reference standard. Methods Literature reviews were performed by members of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis working group on frailty and sarcopenia. Face‐to‐face meetings were organized for the whole group to make amendments and discuss further recommendations. Results A wide range of techniques can be used to assess muscle mass. Cost, availability, and ease of use can determine whether the techniques are better suited to clinical practice or are more useful for research. No one technique subserves all requirements but dual energy X‐ray absorptiometry could be considered as a reference standard (but not a gold standard) for measuring muscle lean body mass. Conclusions Based on the feasibility, accuracy, safety, and low cost, dual energy X‐ray absorptiometry can be considered as the reference standard for measuring muscle mass

The authors reply: Letter on: 'Pitfalls in the measurement of muscle mass: a need for a reference standard' by Clark et al.

However, semantics aside, we think that DXA can indeed serve as a reference standard for measuring muscle mass. Obviously, CT and MRI are advanced techniques that can and have been used to obtain important information such as muscle size/volume and more recently amount and distribution of intra- and intermuscular adipose tissue. Also individual muscles can be assessed separately. However, with respect to muscle mass, the comparison of DXA with CT/MRI is rather difficult because DXA and QCT/MRI measure different physical parameters