Branched dart leaders preceding lightning return strokes Stolzenburg, Maribeth; Marshall, Thomas C.; Karunarathne, Sumedhe ...
Journal of geophysical research. Atmospheres,
16 April 2014, Letnik:
119, Številka:
7
Journal Article
Recenzirano
This study describes the occurrence of branches in lightning dart leaders, based on data acquired in Florida using a high‐speed video camera and electric field change sensors. More than half (57%) of ...72 flashes with analyzable dart leaders show at least one successful branched dart leader (BDL), and nine flashes have two successful BDLs. Overall, 18% of 282 visible successful dart leaders are branched. Most (42 of 50) cases of BDLs occur in the first dart leader after a stepped leader/return stroke sequence, and the data indicate that 55% of first dart leaders are visibly branched. Compared to first dart leaders in the 31 flashes without any branched dart leaders, BDLs tend to follow stepped leader/return strokes with significantly larger average peak currents (−31.3 versus −20.6 kA) and shorter average interstroke intervals (71.94 versus 94.64 ms). Average peak current of BDL strokes is 62% larger (−17.8 versus −11 kA) than that for unbranched first dart leader strokes. Branched dart leaders generally travel in the some of the most recently used lightning channels, but they are not always within the main channel of the prior return stroke. Successful BDLs may dart all the way to ground when in a prior stroke channel, or they may become stepped leaders when they reach the lower end of the prior stroke branch. Electric field change data for all the BDL cases exhibit an erratic pulse character for at least part of the leader duration; in some cases, the erratic character ends when the branches vanish.
Key Points
Video data show 57% of 72 flashes have a successful branched dart leader (BDL)BDLs are often the first dart leaders in a flash and can miss the prior channelRatio of preceding peak current to interstroke interval for BDLs is 2x larger
Homemade Dart Attacks in Hawai’i Balaraman, Prashanth K.; Ng, Karen; Perry, Kyle ...
The American surgeon,
11/2023, Letnik:
89, Številka:
11
Journal Article
Recenzirano
Over a 4.5-year period (September 2014 to March 2019), 7 patients presented to the State’s only Level I Trauma Center with penetrating injuries inflicted by homemade metallic darts. Previously ...described in Micronesia, these are the first domestic cases of assaults utilizing this type of weaponry. Retrospective chart review was conducted for all patients who presented to our institution with a dart injury within the study period. Details regarding demographics, imaging, and patient management were collected and described herein. All 7 patients were male with a median age of 24.6 years impaled with darts that penetrated through the deep muscle and tissue layers of the neck, torso, or extremity. Three patients required operative intervention and no mortalities were observed. The depth of penetration and proximity to vital structures highlight the potential for life-threatening injuries from these homemade darts.
DART is NASA’s demonstration of an asteroid deflection using a kinetic impactor. The spacecraft launched aboard a SpaceX Falcon 9 on November 24th 2021, on a direct collision with the binary asteroid ...system Didymos planned for September 26th 2022. By impacting the small moon, Dimorphos, DART’s objective was to alter the moon’s orbit about the larger asteroid by several minutes.
The navigation of a ballistic mission is usually relatively simple. Other than heading to a violent demise, this mission had a number of unconventional aspects which gave the navigation team interesting challenges: a tight propellant budget for part of the mission, no reaction wheels which resulted in a noisy spacecraft with the Nav team having to rely heavily on Delta Differential One-way Ranging measurements to identify off line-of-sight Delta-V, and critical operations in the last 30 days of the mission under a new thrusting control mode regime. Optical navigation was a critical element in the success of this mission, contributing to the determination of the spacecraft and target ephemerides for refined targeting maneuvers. After strategic decisions in the final weeks of the missions, DART could have comfortably hit the larger asteroid, Didymos, which increased the probably of impact with its moon Dimorphos.
•DART was NASA’s demonstration of an asteroid deflection using a kinetic impactor.•This mission gave the navigation team interesting challenges.•Optical navigation was a critical element in the success of this mission.•DART could have hit Didymos, which increased the probably of impact with its moon.
The rise in improved and widely accessible printing technology has resulted in an interest to develop rapid and minimally destructive chemical analytical techniques that can characterize printing ...inks for forensic document analysis. Chemical characterization of printing inks allows for both discrimination of inks originating from different sources and the association of inks originating from the same source. Direct analysis in real‐time mass spectrometry (DART‐MS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) were used in tandem to analyze four different classes of printing inks: inkjets, toners, offset, and intaglio. A total of 319 samples or ~ 80 samples from each class were analyzed directly on a paper substrate using the two methods. DART‐MS was found to characterize the semi‐volatile polymeric vehicle components, while ATR‐FTIR provided chemical information associated with the bulk components of these inks. Complimentary data results in improved discrimination when both techniques are used in succession resulting in >96% discrimination for all toners, 95% for all inkjets, >92% for all offset, and >54% for all intaglio inks.
Diffusing alpha-emitters radiation Therapy (DaRT) is an interstitial brachytherapy technique using 224Ra seeds. For accurate treatment planning a good understanding of the early DNA damage due to ...α-particles is required. Geant4-DNA was used to calculate the initial DNA damage and radiobiological effectiveness due to α-particles with linear energy transfer (LET) values in the range 57.5–225.9 keV/μm from the 224Ra decay chain. The impact of DNA base pair density on DNA damage has been modelled, as this parameter varies between human cell lines. Results show that the quantity and complexity of DNA damage changes with LET as expected. Indirect damage, due to water radical reactions with the DNA, decreases and becomes less significant at higher LET values as shown in previous studies. As expected, the yield of complex double strand breaks (DSBs), which are harder for a cell to repair, increases approximately linearly with LET. The level of complexity of DSBs and radiobiological effectiveness have been found to increase with LET as expected. The quantity of DNA damage has been shown to increase for increased DNA density in the expected base pair density range of human cells. The change in damage yield as a function of base pair density is largest for higher LET α-particles, an increase of over 50% for individual strand breaks between 62.7 and 127.4 keV/μm. This change in yield shows that the DNA base pair density is an important parameter for modelling DNA damage particularly at higher LET where the DNA damage is greatest and most complex.
•Geant4-DNA simulation of diffusing alpha-emitters radiation therapy (DaRT).•Calculation of initial DNA damage and radiobiological effectiveness (RBE).•Quantity and complexity of DNA damage changes with linear energy transfer (LET).•DNA base pair density has a significant effect on the amount of initial DNA damage.
Textile fibers alone are highly prevalent in our environment, and not only are there a wide variety of fibers, but generally, consumer textiles are colored. Given the variety of crime locations where ...dyes are encountered and the potential circumstances, a rapid, preparation free analysis of samples is highly beneficial. This study has characterized a collection of commercially available textiles dyes by verifying the chemical structure, collecting reference spectra, and developing a method to analyze dyed fibers via Direct Analysis in Real‐Time (DART) mass spectrometry. A methodology for direct analysis of pieces of fabric and single thread samples of polyester fibers dyed with disperse dyes was developed. The presence of 31 target dyes on fibers whose structures were previously established via high‐resolution mass spectrometry was confirmed. Dyed fabrics containing mixtures of dyes in varying concentrations were also evaluated to determine whether each dye in the composition could be detected. The DART‐MS methodology was sensitive and positively characterized disperse dyes in polyester fibers, allowing for blind identification of mixtures with the assistance of a high‐resolution mass spectrometry database.
Darts has evolved from a traditional pub room game to a professional sport. More and more people worldwide are participating in the sport of dart throwing. In order to enhance throwing performance, ...it is important to understand the mechanics of precise dart throwing techniques. Therefore, the purpose of this study was to investigate the fine-tune control of joint kinematics with different vertical targets between different skill levels to understand how to increase the success rate and generate precise fine-tuning of the motor system. Eight advanced players and eight intermediate players participated in this study. A motion capture system measured the kinematic data of the arm during throwing. The results indicated a significant interaction in shoulder internal rotation velocity (p = .031) and elbow supination velocity (p = .047) between advanced and intermediate groups with the different vertical targets. When intermediate players threw darts at different vertical targets, changes in shoulder internal rotation velocity and elbow supination velocity were observed. Conversely, these phenomena were not present in the advanced group. Additionally, we found that dart accuracy or light weight throwing requires an more angle of elbow pronation and generate high angular velocity of wrist palmar flexion during the release process. Based on the findings of this study, these results could provide a reference guide for dart throwing to improve the throwing performance.
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•Reviews recent (2015 – present) applications of DART-MS for forensics.•Drugs, tox, GSR, explosives, fire debris, inks, paints, and lubricants discussed.•Explanation of fundamentals, ...DART-MS variants, and data treatment methods.•Available resources and research needs are also discussed.
The need for rapid chemical analyses and new analytical tools in forensic laboratories continues to grow due to case backlogs, difficult-to-analyze cases, and identification of previously unseen materials such as new psychoactive substances. To adapt to these needs, the forensics community has been pursuing the use of ambient ionization mass spectrometry, and more specifically direct analysis in real time mass spectrometry (DART-MS), for a wide range of applications. From the inception of DART-MS forensic applications have been researched with demonstrations ranging from drugs of abuse to inorganic gunshot residue to printer inks to insect identification. This article presents a review of research demonstrating the use of DART-MS for forensically relevant samples over the past five years. To provide more context, background on the technique, sampling approaches, and data analysis methods are presented along with a discussion on the potential future and research needs of the technology.
The rate of discovery of near-Earth asteroids currently outpaces our ability to analyze them. Knowledge of an asteroid's physical properties is essential to deflect them. I developed free and ...open-source algorithms and training modules. These tools utilize images from robotic telescopes, open-source data, and high school-level mathematics to determine asteroids' size, rotation period, and strength. I took observations of the Didymos binary asteroid, and my algorithm determined its size to be 850 ± 0.04 m, with a 2.261 ± 0.018 h rotation period and rubble-pile strength. I measured a decrease in the mutual orbital period after impact by NASA's 2022 DART Mission, confirming successful deflection. My findings matched closely with those obtained by NASA and external sources (Daly et al., 2023; Thomas et al., 2023; Talbert, 2022, October 11; Nakanoet al., 2022) 1,2,3,4. Every young person and citizen scientist can now be a planetary defender.
•Rate of discovery of near-earth asteroids outpaces current abilities to analyze them.•Open data can help citizen scientists determine asteroid's physical properties.•Algorithms successfully measured success of DART Mission in deflecting Dimorphos.•Citizen scientist participation can provide valuable inputs for planetary defense considerations.
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