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•Analysis of seed-based toxins and seed mashes completed.•DART-MS or one of its variants a was able to detect all 7 compounds in pure form.•Use of high-temperature IRTD-DART-MS was ...required for detection of large molecules.•PCA of mass spectra of seed mashes containing toxins allows for species identification.
Detection of seed-based toxins is a need for forensic chemists when suspected poisonings occur. The evidence that is found is often physically unidentifiable, as the seeds are mashed to extract the toxin. This work investigates potential strategies for rapid detection of seed-based toxins and seed mashes containing these toxins using chemical signatures obtained by direct analysis in real time mass spectrometry (DART-MS). Seven toxins (digoxin, digitoxin, hypaconitine, hyoscyamine, lanatoside, oleandrin, and scopolamine) and six seeds containing these toxins were studied. While detection of four of the toxins was readily attainable, detection of digoxin, digitoxin, and lanatoside was hindered by the inability to thermally desorb these larger compounds under normal operating conditions. The use of DART-MS variants capable of higher desorption temperatures (thermal desorption (TD)-DART-MS and infrared thermal desorption (IRTD)-DART-MS) enabled detection of these compounds. Detection of toxins from direct analysis of seed mashes and methanolic seed mash extracts was found to be compound and technique dependent. Principal component analysis (PCA) of generated mass spectra enabled differentiation of seed species, even in cases where the toxins were undetectable.
The objective of the study is to investigate the effects of enabling value co-creation with consumers on the performance of manufacturing and service SMEs in Poland. The analysis is based on a ...representative sample of 395 firms. Our findings indicate that enabling co-creation does induce positive operational and financial outcomes in both service providers and manufacturers, there are also significant differences in identified patterns and effect sizes. Service firms benefit from engaging in dialog with customers, while manufacturers show the positive influences of enhanced interaction and more choice options. Overall, enabling co-creation has stronger positive effects on service firms than manufacturers in terms of both operational benefits and financial outcomes measured by ROI. This empirical comparison of the effects of employing co-creation enablers by manufacturers and service providers offers original insights into value co-creation theory and supports managers in their choice of instruments for engaging customers.
The dissonant development of positive and negative lightning leaders is a central question in atmospheric electricity. It is also the likely root cause of other reported asymmetries between positive ...and negative lightning flashes, including the ones regarding: stroke multiplicity, recoil activity, leader velocities, and emission of energetic radiation. In an effort to contrast lightning leaders of different polarities, we highlight the staggering differences between two rocket‐triggered lightning flashes. The flash beginning with upward positive leaders exhibits an initial continuous current stage followed by multiple sequences of dart leaders and return strokes. On the other, in its opposite‐polarity counterpart, the upward development of negative leaders is by itself the entire flash. As a result, the flash with negative leaders is faster, briefer, transfers less charge to the ground, has lower currents, and smaller spatial extent. We conclude by presenting a discussion on the three fundamental leader propagation modes.
Plain Language Summary
Lightning flashes that carry positive and negative charges are completely different. In this article, we report on lightning triggered by launching a rocket tethered to the ground toward an electrified cloud. The staggering differences between positive and negative flashes are exposed by a three‐dimensional radio location system and by the current transferred to ground via the trailing wire.
Key Points
Triggered flashes with positive and negative leaders are contrastingly different with the latter being faster, briefer, and more compact
The channel behind triggered positive leaders decays engendering dart leaders and return strokes, which is unparalleled in the negative case
Average conductivity is higher in the negative leader channel despite the lack of return strokes and the lower charge transferred to ground
The dayside equatorial ionospheric electrodynamics exhibit strong variability driven simultaneously by highly changeable external forcings that originate from the solar extreme ultraviolet (EUV), ...magnetosphere, and lower atmosphere. We investigate this variability by carrying out comprehensive data‐driven ensemble modeling using a coupled model of the thermosphere and ionosphere, with the focus on the vertical E × B drift variability during a solar minimum and minor storm period. The variability of vertical E × B drift in response to the changes and uncertainty of primary forcings (i.e., solar EUV, high‐latitude plasma convection and auroral particle precipitation, and lower‐atmospheric tide and wave forcing) is investigated by ensemble forcing sensitivity experiments that incorporate data‐driven stochastic perturbations of these forcings into the model. Second, the impact of assimilating FORMOsa SATellite‐3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT‐3/COSMIC) electron density profiles (EDPs) on the reduction of uncertainty of the modeled vertical E × B drift variability resulting from inadequately specified external forcing is revealed. The Communication and Navigation Outage Forecasting System (C/NOFS) ion drift velocity observations are used for validation. The validation results support the importance of the use of a data‐driven forcing perturbation methods in ensemble modeling and data assimilation. In conclusion, the solar EUV dominates the global‐scale day‐to‐day variability, while the lower atmosphere tide and wave forcing is critical to determining the regional variability. The modeled vertical E × B drift is also sensitive to the magnetospheric forcing. The ensemble data assimilation of FORMOSAT‐3/COSMIC EDPs helps to reduce the uncertainty and improves agreement of the modeled vertical E × B drifts with C/NOFS observations.
Key Points
Ensemble modeling is applied to represent the variability and forcing sensitivity of dayside equatorial E × B drift
FORMOSAT‐3/COSMIC electron density profiles are assimilated to improve ensemble modeling's representation of equatorial E × B drift
Validation with C/NOFS plasma drift supports the importance of data‐based energy inputs in ensemble modeling and data assimilation
Inhibitory interneurons orchestrate prefrontal cortex (PFC) activity, but we have a limited understanding of the molecular and experience-dependent mechanisms that regulate synaptic plasticity across ...PFC microcircuits. We discovered that mGlu5 receptor activation facilitates long-term potentiation at synapses from the basolateral amygdala (BLA) onto somatostatin-expressing interneurons (SST-INs) in mice. This plasticity appeared to be recruited during acute restraint stress, which induced intracellular calcium mobilization within SST-INs and rapidly potentiated postsynaptic strength onto SST-INs. Restraint stress and mGlu5 receptor activation each augmented BLA recruitment of SST-IN phasic feedforward inhibition, shunting information from other excitatory inputs, including the mediodorsal thalamus. Finally, studies using cell-type-specific mGlu5 receptor knockout mice revealed that mGlu5 receptor function in SST-expressing cells is necessary for restraint stress-induced changes to PFC physiology and related behaviors. These findings provide new insights into interneuron-specific synaptic plasticity mechanisms and suggest that SST-IN microcircuits may be promising targets for treating stress-induced psychiatric diseases.
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•Restraint stress activates PFC SST-INs•Restraint stress enhances excitatory drive onto SST-INs and feedforward inhibition•mGlu5 receptors regulate LTP on SST-INs•SST-mGlu5−/− mice display unique stress-related behavioral adaptations
Joffe et al. demonstrated that restraint stress rapidly potentiates excitatory transmission onto prefrontal cortex somatostatin interneurons in mice, biasing information processing toward amygdala-driven feedforward inhibition. The authors pinpoint metabotropic glutamate mGlu5 receptor plasticity on somatostatin interneurons as an essential mediator of microcircuit modifications and discrete behavioral adaptations following acute stress.
The development of quantitative and qualitative analytical methods to assess micro-plastics (MPLs) and nano-plastics (NPLs) content in the environment is a central issue for realistic risk assessment ...studies. However, the quantitative analysis continues being a critical issue, in particular for MPLs from 100 μm down to the nano-sized range in complex environmental samples.
This paper evaluates the potential of mass spectrometry for the analysis of MPLs and NPLs. The performance of different techniques including matrix-assisted laser desorption ionisation (MALDI) coupled to time-of-flight mass spectrometry (TOF-MS), liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS), and the ambient ionisation approaches as desorption electrospray ionisation (DESI) and direct analysis real-time (DART), were assessed for the study of polystyrene (PS) MPLs and NPLs in natural waters.
A method based on LC-HRMS, equipped with an atmospheric pressure photoionisation source (APPI), operated in negative conditions for the quantitative analysis of PS MPLs and NPLs in natural waters, was developed. The chromatographic separation was achieved using an advanced polymer chromatographic (APC) column using toluene isocratic as the mobile phase. The optimal analytical method showed an instrumental limit of detection (ILOD) of 20 pg and methods limits of detection and quantification around 30 pg L−1 and 100 pg L−1, respectively. And, recoveries of 60 and 70% in samples from rivers and the marine coast, respectively. The performance of the new method was proved by the analysis of fortified samples and natural seawater samples.
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•LC-APPI(−)HRMS method for the quantitative analysis of polystyrene microplastics.•LC separation was achieved using an advanced polymer chromatographic (APC) column.•The instrumental limit of detection (ILOD) was 20 pg.
Because of the rich omega-3 fatty acids content, harp seal (Pagophilus groenlandicus) oil is a popular supplement that is packaged as pills in Canada and sold for medicinal purposes, although this ...practice is banned in the United States. Due to US regulations, it is important to be able to distinguish between fish oil and seal oil, but the taxonomic determination of oils provenance has been a difficult problem to solve. In this study, Direct Analysis in Real Time time-of-flight mass spectrometry (DART TOFMS) was used to analyze the chemotypes of blubber samples collected from seven species of marine mammals, including seals, sea lions, and a porpoise. Results indicated that the chemotype profiles found in negative-ion mode could be used to separate all of the species using Discriminant Analysis of Principal Components (DAPC). Consequently, this study suggests that it may be possible to identify the taxonomic source of marine mammal oils based on chemical chemotypes.
•Determining taxonomic source of oil is needed to enforce wildlife laws.•DNA analysis for determining species source of an oil has not yielded results.•Determination of species of oil can be accomplished using mass spectrometry.•Analysis is based on the presence of fatty acids, sterols and glycerols.•Ambient ionization coupled to chemometrics can be used to determine the origin of marine mammals.
Background
Diffusing alpha‐emitters radiation therapy (DaRT) is a novel brachytherapy technique that leverages the diffusive flow of 224Ra progeny within the tumor volume over the course of the ...treatment. Cell killing is achieved by the emitted alpha particles that have a short range in tissue and high linear energy transfer. The current proposed absorbed dose calculation method for DaRT is based on a diffusion‐leakage (DL) model that neglects absorbed dose from beta particles.
Purpose
This work aimed to couple the DL model with dose point kernels (DPKs) to account for dose from beta particles as well as to consider the non‐local deposition of energy.
Methods
The DaRT seed was modeled using COMSOL multiphysics and the DL model was implemented to extract the spatial information of the diffusing daughters. Using Monte–Carlo (MC) methods, DPKs were generated for 212Pb, 212Bi, and their progenies since they were considered to be the dominant beta emitters in the 224Ra radioactive decay chain. A convolution operation was performed between the integrated number densities of the diffusing daughters and DPKs to calculate the total absorbed dose over a 30‐day treatment period. Both high‐diffusion and low‐diffusion cases were considered.
Results
The calculated DPKs showed non‐negligible energy deposition over several millimeters from the source location. An absorbed dose >10 Gy was deposited within a 1.8 mm radial distance for the low diffusion case and a 2.2 mm radial distance for the high diffusion case. When the DPK method was compared with the local energy deposition method that solely considered dose from alpha particles, differences above 1 Gy were found within 1.3 and 1.8 mm radial distances from the surface of the source for the low diffusion and high diffusion cases, respectively.
Conclusions
The proposed method enhances the accuracy of the dose calculation method used for the DaRT technique.
As the challenges faced by drug chemists persist, due to the presence of emerging drugs, laboratories continue to look for new solutions, ranging from existing methods to implementation of entirely ...new technology. A common barrier for making workflow changes is a lack of pre‐existing data demonstrating the potential impact of these changes. In this study, we compare, qualitatively and quantitatively, an existing workflow for seized drug analysis to an experimental workflow. Four chemists were asked to analyze a total of 50 mock case samples across the two workflows. The existing workflow employed color tests for screening alongside general purpose GC‐FID and GC‐MS analyses for confirmation. The experimental workflow combined DART‐MS screening with class‐specific (targeted) GC‐MS analysis for confirmation. Comparison of the workflows showed that screening by DART‐MS required the same amount of time as color tests but yielded more accurate and specific information. Confirmation using the existing workflow required more than twice the amount of instrument time and data interpretation time while also presenting other analytical challenges that prevented compound confirmation in select samples. Targeted GC‐MS methods simplified data interpretation, reduced consumption of reference materials, and addressed almost all limitations of general‐purpose methods. While the experimental workflow requires modifications and answering of additional research questions, this study shows how rethinking analytical workflows for seized drug analysis could reduce turnaround times, backlogs, and standards consumption. It also demonstrates the potential impact of being able to investigate workflow changes prior to implementation.
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