In recent months, there has been increased reporting of seized drug and toxicology cases containing rodenticides, the active ingredient in rat poisons. Seeing as rodenticides are not scheduled ...substances, they are not commonly screened for in seized drug analysis. This work investigates the use of TD‐DART‐MS for the simultaneous detection of rodenticides and drugs. Six rodenticides were evaluated, an optimal method was established, and limits of detection in the tens of nanograms were calculated. Additional studies highlight that detection at less than 1% by weight in mixtures with AB‐FUBINACA, cocaine, heroin, or methamphetamine was possible. This work presents an optimized method for detection of these compounds, allowing for the simultaneous detection of drugs and rodenticides, providing drug chemists with a tool for rapid identification of these compounds for forensic or public health purposes.
Genetic diversity is frequently described using heterozygosity, particularly in a conservation context. Often, it is estimated using single nucleotide polymorphisms (SNPs); however, it has been shown ...that heterozygosity values calculated from SNPs can be biased by both study design and filtering parameters. Though solutions have been proposed to address these issues, our own work has found them to be inadequate in some circumstances. Here, we aimed to improve the reliability and comparability of heterozygosity estimates, specifically by investigating how sample size and missing data thresholds influenced the calculation of autosomal heterozygosity (heterozygosity calculated from across the genome, i.e. fixed and variable sites). We also explored how the standard practice of tri‐ and tetra‐allelic site exclusion could bias heterozygosity estimates and influence eventual conclusions relating to genetic diversity. Across three distinct taxa (a frog, Litoria rubella; a tree, Eucalyptus microcarpa; and a grasshopper, Keyacris scurra), we found heterozygosity estimates to be meaningfully affected by sample size and missing data thresholds, partly due to the exclusion of tri‐ and tetra‐allelic sites. These biases were inconsistent both between species and populations, with more diverse populations tending to have their estimates more severely affected, thus having potential to dramatically alter interpretations of genetic diversity. We propose a modified framework for calculating heterozygosity that reduces bias and improves the utility of heterozygosity as a measure of genetic diversity, whilst also highlighting the need for existing population genetic pipelines to be adjusted such that tri‐ and tetra‐allelic sites be included in calculations.
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•Detection of fentanyl and 16 analogues is possible using both TD-DART-MS and IMS.•Fentanyl can be detected in the presence of 1000× heroin with no signal reduction.•Fentanyl and ...heroin can be detected in the presence of background matrices.•Nanogram quantities can be detected by sampling residues off a plastic bag.
Fentanyl and fentanyl analogues represent a current and emerging threat in the United States as pure illicit narcotics and in mixtures with heroin. Because of their extreme potency, methods to safely and rapidly detect these compounds are of high interest. This work investigates the use of thermal desorption direct analysis in real time mass spectrometry (TD-DART-MS) and ion mobility spectrometry (IMS) as tools for the rapid and sensitive (nanogram to picograms) detection of fentanyl, 16 fentanyl analogues, and five additional opioids. Competitive ionization studies highlight that detection of these compounds in the presence of heroin is readily achievable, down to 0.1% fentanyl by mass with TD-DART-MS. With IMS, detection of nanogram levels of fentanyl in a binary fentanyl and heroin mixture is possible but can be complicated by decreased resolution in certain commercial instrument models. Modifications to the alarm windows can be used to ensure detection of fentanyl in binary mixtures. Additionally, three complex background matrices (fingerprint residue, dirt, and plasticizers) are shown to have a minimal effect of the detection of these compounds. Wipe sampling of the exterior of bags of questioned powders is shown to be a safe alternative method for field screening and identification, removing the need to handle potentially lethal amounts of material.
A negative lightning flash with 16 leader‐return stroke sequences, triggered in the summer of 2013 using the classical rocket‐and‐wire triggering technique, was examined with simultaneous ...two‐dimensional (2D) imaging of very high‐frequency (VHF) radiation sources, channel‐base current measurement, broadband electric field waveforms and high‐speed video images. A total of 28.0 C negative charge was transferred to ground during the whole flash, and the charge transferred during the initial stage was 4.9 C, which is the weakest among the triggered lightning flashes at the SHandong Artificially Triggering Lightning Experiment (SHATLE). The peak current of 16 return strokes ranged from 5.8 to 32.5 kA with a geometric mean of 14.1 kA. The progression of upward positive leader and downward negative (dart or dart‐stepped) leaders was reproduced visually by using an improved short‐baseline VHF lightning location system with continuous data recording capability. The upward positive leader was mapped immediately from the tip of the metal wire during the initial stage, developing at a speed of about 104 m/s without branches. The upward positive leader and all the 14 negative leaders captured by the 2D imaging system propagated along the same channel with few branches inside the cloud, which might be the reason for the relatively small charge transfer. The 2D imaging results also show that dart leaders may transform into dart‐stepped leaders after a long time interval between successive strokes.
Key Points
The VHF location system was developed with continuous recording capabilityThe upward positive leader developed at a speed of about 104 m/sDart leaders may transform into dart‐stepped leaders after a long time interval
Forests substantially mediate the water and carbon dioxide exchanges between terrestrial ecosystems and the atmosphere. The rate of this exchange, including evapotranspiration (ET) and gross primary ...production (GPP), depends mainly on the underlying vegetation type, health state, and the composition of abiotic environmental drivers. However, the complex 3D structure of forest canopies and the inherent top-view perspective of optical and thermal remote sensing complicate remote sensing-based retrievals of biotic and abiotic factors that eventually determine ET and GPP. This study investigates the sensitivity of remote sensing approaches to 3D variation of abiotic and biotic environmental drivers. We use 3D virtual scenes of two structurally different Swiss forests and the radiative transfer model DART to simulate the 3D distribution of solar irradiance and reflected radiance in the forest canopy. These simulations, in combination with LiDAR data, are used to derive the absorbed photosynthetic active radiation (APAR) and the leaf area index (LAI) in 3D space. The 3D variation of both parameters was quantified and analyzed. We then simulated images of the top-of-canopy bi-directional reflectance factor (BRF) and compared them with the hemispheric-conical reflectance factor (HCRF) data derived from HyPlant airborne imaging spectrometer measurements. The simulated BRF data was used to derive APAR and LAI, and the results were compared to their respective 3D representations. We unravel considerable spatial differences between both representations. We discuss possible reasons for the disagreement, including a potential insensitivity of the inherent top-of-canopy view for the real 3D product dynamics and limitations of the processing of remote sensing data, especially the approximation of effective surface irradiance. Our results can help understanding sources of uncertainties in remote sensing based gas exchange products and defining mitigation strategies.
•Virtual scenes indicate large 3D variations in both LAI and APAR.•LAI and APAR derived from remote sensing differ from 3D representations.•Top-of-canopy perspective has limited sensitivity for 3D dynamics.•Shadows in the canopy affect both LAI and APAR calculations.•Assumed constant irradiance partly explains LAI and APAR uncertainties.
We report on the development of an easily deployable LF near‐field interferometric‐time of arrival (TOA) 3‐D Lightning Mapping Array applied to imaging of entire lightning flashes. An interferometric ...cross‐correlation technique is applied in our system to compute windowed two‐sensor time differences with submicrosecond time resolution before TOA is used for source location. Compared to previously reported LF lightning location systems, our system captures many more LF sources. This is due mainly to the improved mapping of continuous lightning processes by using this type of hybrid interferometry/TOA processing method. We show with five station measurements that the array detects and maps different lightning processes, such as stepped and dart leaders, during both in‐cloud and cloud‐to‐ground flashes. Lightning images mapped by our LF system are remarkably similar to those created by VHF mapping systems, which may suggest some special links between LF and VHF emission during lightning processes.
Key Points
An interferometric‐TOA LF 3‐D Lightning Mapping Array was designed and appliedMapped and measured stepped and dart leaders from both IC and CG flashesImaged entire LF structure of different flashes which is similar as VHF maps
Background
Diffusing alpha‐emitters radiation therapy (“Alpha‐DaRT”) is a new method for treating solid tumors with alpha particles, relying on the release of the short‐lived alpha‐emitting daughter ...atoms of radium‐224 from interstitial sources inserted into the tumor. Alpha‐DaRT tumor dosimetry is governed by the spread of radium's progeny around the source, as described by an approximate framework called the “diffusion‐leakage model”. The most important model parameters are the diffusion lengths of radon‐220 and lead‐212, and their estimation is therefore essential for treatment planning.
Purpose
Previous works have provided initial estimates for the dominant diffusion length, by measuring the activity spread inside mice‐borne tumors several days after the insertion of an Alpha‐DaRT source. The measurements, taken when lead‐212 was in secular equilibrium with radium‐224, were interpreted as representing the lead‐212 diffusion length. The aim of this work is to provide first experimental estimates for the diffusion length of radon‐220, using a new methodology.
Methods
The diffusion length of radon‐220 was estimated from autoradiography measurements of histological sections taken from 24 mice‐borne subcutaneous tumors of five different types. Unlike previous studies, the source dwell time inside the tumor was limited to 30 min, to prevent the buildup of lead‐212. To investigate the contribution of potential non‐diffusive processes, experiments were done in two sets: fourteen in vivo tumors, where during the treatment the tumors were still carried by the mice with active blood supply, and 10 ex‐vivo tumors, where the tumors were excised before source insertion and kept in a medium at 37∘C$37^\circ {\text{C}}$ with the source inside.
Results
The measured diffusion lengths of radon‐220, extracted by fitting the recorded activity pattern up to 1.5 mm from the source, lie in the range 0.25−0.6mm${0.25-0.6}\nobreakspace {\text{mm}}$, with no significant difference between the average values measured in in‐vivo and ex‐vivo tumors: LRnin−vivo=0.40±0.08mm$L_{Rn}^{in-vivo}=0.40{\pm }0.08\nobreakspace {\text{mm}}$ versus LRnex−vivo=0.39±0.07mm$L_{Rn}^{ex-vivo}=0.39{\pm }0.07\nobreakspace {\text{mm}}$. However, in‐vivo tumors display an enhanced spread of activity 2–3 mm away from the source. This effect is not explained by the current model and is much less pronounced in ex‐vivo tumors.
Conclusions
The average measured radon‐220 diffusion lengths in both in‐vivo and ex‐vivo tumors are consistent with published data on the diffusion length of radon in water and lie close to the upper limit of the previously estimated range of 0.2−0.4mm$0.2-0.4\nobreakspace {\text{mm}}$. The observation that close to the source there is no apparent difference between in‐vivo and ex‐vivo tumors, and the good agreement with the theoretical model in this region suggest that the spread of radon‐220 is predominantly diffusive in this region. The departure from the model prediction in in‐vivo tumors at large radial distances may hint at potential vascular contribution, which will be the subject of future works.
The comparison of DART-QTOF and LC-ESI-QTOF was studied on the discrimination of beef from different origins based on lipidomics. Compared to LC-ESI-QTOF (+), DART-QTOF (+) is particularly suitable ...for smaller compounds analysis, and has better repeatability and stability. The data were screened based on detection rate, RSD value, fold change and P value, and library matching to obtain 852 and 879 raw peaks, 62 and 165 differential peaks and 17 and 25 potential markers in DART-QTOF (+) and LC-ESI-QTOF (+), respectively. Then, support vector machine (SVM) was constructed based on them and LC-ESI-QTOF (+) was superior to DART-QTOF (+) in SVM models, achieving a highest training accuracy of 100% and a validation accuracy of 89.91%. Based on LC-ESI-QTOF (+) and LC-ESI-QTOF (−), 40 potential markers were found, and beef samples from Canada, Argentina and New Zealand shared higher similarity, while beef samples from Brazil, Australia and Uruguay had more similarities. Considering the high efficiency, repeatability and stability of DART-QTOF acquisition, it is necessary to optimize its data acquisition and processing methods, in order to realize the faster assessment for lipidomics as well as food authenticity in the future.
•DART-QTOF acquisition has better reproducibility and stability.•LC-ESI-QTOF was superior to DART-QTOF in SVM models.•DART-QTOF could realize the faster assessment for lipidomics as well as food authenticity in the future.
•DART with Agilent iFunnel-QTOF limited match to DART/JEOL-TOF-MS ForeST Database.•GC/QTOF and LC/QTOF success in Dalbergia wood species identification.•Novel inclusion of ES- mode ionization to ...complement ES+ and EI+ modes.•Machine learning with statistical analysis replaces manual ion identification.•Application suited to legally defensible wood genus and species identification.
Illegal logging and trafficking of endangered timber species has attracted the world's major organized crime groups, with associated deforestation and serious social damage. The inability of traditional methodologies and DNA analysis to readily perform wood identification to the species level for monitoring has stimulated research on chemotyping techniques. In this study, simple wood extraction of endangered rosewoods (Dalbergia spp), amenable to use in the field, produced colorful hues that were suggestive of wood species. A more definitive study was conducted to develop wood species identification procedures using high-resolution quadrupole time-of-flight (QTOF) mass spectrometers interfaced with liquid chromatography (LC), gas chromatography (GC), and Direct Analysis in Real Time (DART). The time consuming process of extracting “identifying” mass spectral ions for species identification, contentious due to their ubiquitous nature, was supplanted by application of machine learning processes. The unbiased software mining of raw data from multiple analytical batches, followed by statistical Random Forest analysis, enabled discrimination between both anatomically and chemotypically similar Dalbergia species. Statistical Principal Component Analysis (PCA) scatterplots with 95% confidence ellipses were visually compelling in showing a differential clustering of Dalbergia from other commonly traded and lookalike wood species. The information rich raw data from GC or LC analyses offered a corroborative, legally defensible, and widely available confirmatory tool in the identification of timber species.
The colorful hues of Dalbergia rosewood extracts Display omitted
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