Primary Fragments Research Articles

Monte Carlo simulation of the measurement by the 2E technique of the average prompt neutron multiplicity as a function of the mass of fragments from thermal neutron-induced fission of 239Pu

Using a Monte Carlo method, we simulate the measurement, by the 2E technique, of the average prompt neutron multiplicity as a function of the mass of fragments from the thermal neutron-induced fission of 239Pu. The input data for the simulation, associated with the primary fragment mass (A), consist of the yield (Y), the distribution of the total kinetic energy characterized by its average ((TKE) ̅) and its standard deviation (σ_TKE), the average prompt neutron multiplicity (ν ̅_s, a sawtooth approach of experimental data), and the slope of neutron multiplicity against total kinetic energy (dν_s/d<TKE>). The output data, associated with the simulated as the fragment mass measured by the 2E technique (µ), consist of the yield (y), the distribution of the total kinetic energy characterized by its average ((tke) ̅) and its standard deviation (σ_tke), and the average prompt neutron multiplicity (ν ̅_µ). In the mass regions A≈115 and A>150, ν ̅_µ is higher than ν ̅_s. This result suggests that, in those mass regions, the 2E experimental values associated with the average neutron multiplicity are overestimated, referred to the corresponding to the primary fragments.

Unimolecular thermal decarbonylation of vanillin stifled by the bimolecular reactivity of methyl-loss intermediate

We studied the thermal decomposition of vanillin in a low-pressure pyrolysis microreactor by photoelectron photoion coincidence spectroscopy. The pyrolysis products were identified isomer-selectively by photoion mass-selected threshold photoelectron spectra (ms-TPES) based on Franck–Condon simulations and reference spectra. Methyl loss by homolytic C–O bond fission in the methoxy group is the initial unimolecular decomposition step. The primary intermediate, the 2-hydroxy-5-formyl-phenoxy radical (m/z 137), may undergo multiple decarbonylation steps and lose a hydrogen atom sequentially to finally form but-1-ene-3-yne at m/z 52. The ms-TPES and calculated reaction path energetics identified the product intermediates at masses of 109, 108, 81, and 80 amu. 3,4-Dihydroxybenzaldehyde (m/z 138) and 3,4-dioxocyclohexa-1,5-diene-1-carbaldehyde (m/z 136) peaks do not correspond to unimolecular decomposition products. Instead, they are formed in the hydrogen-transfer self-reaction of the primary methyl-loss fragment of vanillin at m/z 137. 3,4-Dihydroxybenzaldehyde is thermally more stable than vanillin, as also shown by its high activation energy to decomposition to m/z 137, 110 and 82 fragments. The lighter m/z 136 bimolecular product is prone to CO loss and its reaction path merges with the H-loss-containing unimolecular decomposition channel of vanillin. Further bimolecular reactions are also discussed. These mechanistic insights, especially the high (self-)reactivity of the methyl-loss intermediate and the resulting preponderance of bimolecular chemistry leading to inert dihydroxybenzaldehyde will guide process design involving vanillin and vanillin-like feedstocks.

Structures of Endocrine-Disrupting Chemicals Correlate with the Activation of 12 Classic Nuclear Receptors.

Endocrine-disrupting chemicals (EDCs) can inadvertently interact with 12 classic nuclear receptors (NRs) that disrupt the endocrine system and cause adverse effects. There is no widely accepted understanding about what structural features make thousands of EDCs able to activate different NRs as well as how these structural features exert their functions and induce different outcomes at the cellular level. This paper applies the hierarchical characteristic fragment methodology and high-throughput screening molecular docking to comprehensively explore the structural and functional features of EDCs for the 12 NRs based on more than 7000 chemicals from curated datasets. EDCs share three levels of key fragments. The primary and secondary fragments are associated with the binding of EDCs to four groups of receptors: steroidal nuclear receptors (SNRs, including androgen, estrogen, glucocorticoid, mineralocorticoid, and progesterone), retinoic acid receptors, thyroid hormone receptors, and vitamin D receptors. The tertiary fragments determine the activity type by interacting with two key locations in the ligand-binding domains of NRs (N-H5-H3-C and N-H7-H11-C for SNRs and N-H5-H5'-H2'-H3-C and N-H6'-H11-C for non-SNRs). The resulting compiled structural fragments of EDCs together with elucidated compound NR binding modes provide a framework for understanding the interactions between EDCs and NRs, facilitating faster and more accurate screening of EDCs for multiple NRs in the future.

Identification of Inhibitors of Cholesterol Transport Proteins Through the Synthesis of a Diverse, Sterol‐Inspired Compound Collection

AbstractCholesterol transport proteins regulate a vast array of cellular processes including lipid metabolism, vesicular and non‐vesicular trafficking, organelle contact sites, and autophagy. Despite their undoubted importance, the identification of selective modulators of this class of proteins has been challenging due to the structural similarities in the cholesterol‐binding site. Herein we report a general strategy for the identification of selective inhibitors of cholesterol transport proteins via the synthesis of a diverse sterol‐inspired compound collection. Fusion of a primary sterol fragment to an array of secondary privileged scaffolds led to the identification of potent and selective inhibitors of the cholesterol transport protein Aster‐C, which displayed a surprising preference for the unnatural‐sterol AB‐ring stereochemistry and new inhibitors of Aster‐A. We propose that this strategy can and should be applied to any therapeutically relevant sterol‐binding protein.

Identification of Inhibitors of Cholesterol Transport Proteins Through the Synthesis of a Diverse, Sterol-Inspired Compound Collection.

Cholesterol transport proteins regulate a vast array of cellular processes including lipid metabolism, vesicular and non-vesicular trafficking, organelle contact sites, and autophagy. Despite their undoubted importance, the identification of selective modulators of this class of proteins has been challenging due to the structural similarities in the cholesterol-binding site. Herein we report a general strategy for the identification of selective inhibitors of cholesterol transport proteins via the synthesis of a diverse sterol-inspired compound collection. Fusion of a primary sterol fragment to an array of secondary privileged scaffolds led to the identification of potent and selective inhibitors of the cholesterol transport protein Aster-C, which displayed a surprising preference for the unnatural-sterol AB-ring stereochemistry and new inhibitors of Aster-A. We propose that this strategy can and should be applied to any therapeutically relevant sterol-binding protein.

Analysis of Five Mushroom Toxins in Blood by UPLC-HRMS.

To develop a method for the simultaneous and rapid detection of five mushroom toxins (α-amanitin, phallacidin, muscimol, muscarine and psilocin) in blood by ultra-high performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). The blood samples were precipitated with acetonitrile-water solution(Vacetonitril∶Vwater=3∶1) and PAX powder, then separated on ACQUITY Premier C18 column, eluted gradient. Five kinds of mushroom toxins were monitored by FullMS-ddMS2/positive ion scanning mode, and qualitative and quantitative analysis was conducted according to the accurate mass numbers of primary and secondary fragment ions. All the five mushroom toxins had good linearity in their linear range, with a determination coefficient (R2)≥0.99. The detection limit was 0.2-20 ng/mL. The ration limit was 0.5-50 ng/mL. The recoveries of low, medium and high additive levels were 89.6%-101.4%, the relative standard deviation was 1.7%-6.7%, the accuracy was 90.4%-101.3%, the intra-day precision was 0.6%-9.0%, the daytime precision was 1.7%-6.3%, and the matrix effect was 42.2%-129.8%. The method is simple, rapid, high recovery rate, and could be used for rapid and accurate qualitative screening and quantitative analysis of various mushroom toxins in biological samples at the same time, so as to provide basis for the identification of mushroom poisoning events.

Clustering of electromagnetic showers and particle interactions with graph neural networks in liquid argon time projection chambers

Liquid argon time projection chambers (LArTPCs) are a class of detectors that produce high resolution images of charged particles within their sensitive volume. In these images, the clustering of distinct particles into superstructures is of central importance to the current and future neutrino physics program. Electromagnetic (EM) activity typically exhibits spatially detached fragments of varying morphology and orientation that are challenging to efficiently assemble using traditional algorithms. Similarly, particles that are spatially removed from each other in the detector may originate from a common interaction. Graph neural networks (GNNs) were developed in recent years to find correlations between objects embedded in an arbitrary space. The graph particle aggregator (GrapPA) first leverages GNNs to predict the adjacency matrix of EM shower fragments and to identify the origin of showers, i.e., primary fragments. On the PILArNet public LArTPC simulation dataset, the algorithm achieves a shower clustering accuracy characterized by a mean purity of 99.4%, a mean efficiency of 99.6% and a primary identification accuracy of 99.8%. It yields a relative shower energy uncertainty of $(4.1+1.4/\sqrt{E(\mathrm{GeV})})%$ and a shower direction uncertainty of $(2.1/\sqrt{E(\mathrm{GeV})})\ifmmode^\circ\else\textdegree\fi{}$. The optimized algorithm is then applied to the related task of clustering particle instances into interactions and yields a mean purity of 99.8% and a mean efficiency of 99.5% for an interaction density of $\mathcal{O}(1)\text{ }\text{ }{\mathrm{m}}^{\ensuremath{-}3}$.

Bat phylogenetic responses to regenerating Amazonian forests

AbstractThroughout the tropics, regenerating secondary forests occupy vast areas previously cleared for agriculture and cattle ranching. However, despite the importance of regenerating forests in mitigating the pervasive negative consequences of forest loss and fragmentation on forest‐associated biodiversity, longitudinal studies on species' phylogenetic responses to matrix regeneration are rare.We surveyed bats in continuous primary forest, primary forest fragments and in the regenerating secondary forest matrix of a whole‐ecosystem Amazonian fragmentation experiment, ~15 and ~30 years after forest clearance, to investigate how changes in matrix quality through forest recovery affect phylogeneticα‐ andβ‐diversity.We found that temporal changes in phylogeneticα‐richness were more marked in the secondary forest matrix than in forest fragments and continuous forest, evidencing a significant increase in total evolutionary history over time. However, when the effects of species richness were accounted for, the phylogenetic structure of each assemblage was reduced close to zero, evincing a random pattern of lineages in all habitat types. Temporal differences in phylogeneticβ‐diversity were driven mainly byβreplacementin secondary forest and continuous forest ~30 years after forest clearance. Both habitats also clustered together in terms ofβrichness, indicating similar levels of evolutionary heritage. Consequently, regenerating secondary forest showed a reduction in the extinction probability of lineages over time.Synthesis and applications. Approximately 30 years of secondary forest regeneration were sufficient for phylogenetic richness to recover to levels similar to those observed in continuous forest. Promoting forest succession on degraded land through a combination of natural and active restoration, while ensuring the long‐term protection of secondary forests regardless of their age, is of key importance for conserving tropical bat diversity and their associated ecosystem services. Such restoration measures would stimulate the recolonization of fragments and matrix habitats by evolutionarily distinct bat species, safeguarding phylogenetically diverse assemblages and ecological functions. Our study suggests that forest restoration in tropical degraded areas should be encouraged and secondary forests be protected by law, especially in countryside ecosystems with high primary forest cover, and in the surroundings of protected areas.

Litter thickness and soil pH influence the diversity of saprotrophic fungi in primary forest fragments in the Amazon

Plant communities influence the composition of local fungi, and this has been verified in different biomes around the world. The analysis of the litter structure in a forest reserve in the Amazon has shown that floristic diversity and substrate morphology affect fungal diversity at different scales. Our results revealed that the α diversity of the fungi was positively correlated with the substrate quality in the litter, while β diversity showed differences within and among the floristic groups identified in the reserve. In addition to litter morphology, some soil physicochemical variables were considered as predictors, of which only the soil pH affected the fungal richness. Therefore, our results support the hypotheses that: 1) plant identity and substrate deposition time in soil have an effect on microbial communities, and 2) a greater leaf diversity correlates to increased fungal variety.

Biological Impact of Target Fragments on Proton Treatment Plans: An Analysis Based on the Current Cross-Section Data and a Full Mixed Field Approach.

Simple SummaryProton therapy is now an established external radiotherapy modality for cancer treatment. Clinical routine currently neglects the radiobiological impact of nuclear target fragments even if experimental evidences show a significant enhancement in cell-killing effect due to secondary particles. This paper quantifies the contribution of proton target fragments of different charge in different irradiation scenarios and compares the computationally predicted corrections to the overall biological dose with experimental data.Clinical routine in proton therapy currently neglects the radiobiological impact of nuclear target fragments generated by proton beams. This is partially due to the difficult characterization of the irradiation field. The detection of low energetic fragments, secondary protons and fragments, is in fact challenging due to their very short range. However, considering their low residual energy and therefore high LET, the possible contribution of such heavy particles to the overall biological effect could be not negligible. In this context, we performed a systematic analysis aimed at an explicit assessment of the RBE (relative biological effectiveness, i.e., the ratio of photon to proton physical dose needed to achieve the same biological effect) contribution of target fragments in the biological dose calculations of proton fields. The TOPAS Monte Carlo code has been used to characterize the radiation field, i.e., for the scoring of primary protons and fragments in an exemplary water target. TRiP98, in combination with LEM IV RBE tables, was then employed to evaluate the RBE with a mixed field approach accounting for fragments’ contributions. The results were compared with that obtained by considering only primary protons for the pristine beam and spread out Bragg peak (SOBP) irradiations, in order to estimate the relative weight of target fragments to the overall RBE. A sensitivity analysis of the secondary particles production cross-sections to the biological dose has been also carried out in this study. Finally, our modeling approach was applied to the analysis of a selection of cell survival and RBE data extracted from published in vitro studies. Our results indicate that, for high energy proton beams, the main contribution to the biological effect due to the secondary particles can be attributed to secondary protons, while the contribution of heavier fragments is mainly due to helium. The impact of target fragments on the biological dose is maximized in the entrance channels and for small values. When applied to the description of survival data, model predictions including all fragments allowed better agreement to experimental data at high energies, while a minor effect was observed in the peak region. An improved description was also obtained when including the fragments’ contribution to describe RBE data. Overall, this analysis indicates that a minor contribution can be expected to the overall RBE resulting from target fragments. However, considering the fragmentation effects can improve the agreement with experimental data for high energy proton beams.

Energy dependent calculations of fission product, prompt, and delayed neutron yields for neutron induced fission on 235U, 238U, and 239Pu

ABSTRACT We perform energy-dependent calculations of independent and cumulative fission product yields for , , and in the first chance fission region. Starting with the primary fission fragment distributions taken from available experimental data and analytical functions based on assumptions for the excitation energy and spin-parity distributions, the Hauser-Feshbach statistical decay treatment for fission fragment de-excitation is applied to more than 1,000 fission fragments for the incident neutron energies up to 5 MeV. The calculated independent yields are then used as an input of -decay calculations to produce the cumulative yield, and summation calculations are performed. Model parameters in these procedures are adjusted by applying the Bayesian technique at the thermal energy for and and in the fast energy range for . The calculated fission observable quantities, such as the energy-dependent cumulative yields, and prompt and delayed neutron yields, are compared with available experimental data. We also study the possible impact of the second chance fission opening on the energy dependence of the delayed neutron yield by on the opening of second chance fission on the energy dependence calculation.

Limonoids with Diverse Oxidation Patterns of C-12 Indicating a Complete Ring C-seco Biogenetic Pathway from Munronia unifoliolata.

Munrolins A-Q (1-17), 17 new ring C-seco limonoids with diverse oxidative patterns of C-12, together with nine known analogues (18-26), were isolated from the CH2Cl2 extract of Munronia unifoliolata. The planar structures were elucidated by a combination of 1D and 2D NMR and HR-MS analyses, while the absolute configurations were confirmed by ECD calculations and single-crystal X-ray diffraction. Munrolins A (1) and B (2) were first identified as ring C-seco limonoids with a 12,13-ether bridge moiety. Munrolins C-J (3-10) have a rare reduced primary alcohol fragment, while munrolin Q (17) has an unusual ketal fragment formed by dehydration of C-12/14. These limonoids with diverse alcohol and aldehyde type C11/12 branches may be generated through different degrees of reduction after the Baeyer-Villiger oxidation at the C ring, as key intermediates to supplement the biogenetic pathway of ring C-seco limonoids. Compounds 11, 19, and 26 could reverse the multidrug resistance of MCF-7/doxorubicin cells with reversal fold values of 5.2, 4.5, and 18.3, respectively.

Visible Light Induced Cu-Catalyzed Asymmetric C(sp3)-H Alkylation.

The asymmetric functionalization of C-H is one of the most attractive strategies in asymmetric synthesis. In the past decades, catalytic enantioselective C(sp3)-H functionalization has been intensively studied and successfully applied in various asymmetric bond formations, whereas asymmetric C(sp3)-H alkylation was not well developed. Photoredox catalysis has recently emerged as an efficient way to synthesize organic compounds under mild conditions. Despite many photoinduced stereoselective reactions that have been achieved, the related enantioselective C(sp3)-C(sp3) coupling is challenging, especially of the photocatalytic asymmetric C(sp3)-H radical alkylation. Here, we report a visible light induced Cu catalyzed asymmetric sp3 C-H alkylation, which is effective for coupling with unbiased primary, secondary, and tertiary alkyl fragments in high enantioselectivities. This reaction would provide a new approach for the synthesis of important molecules such as unnatural α-amino acids and late-stage functionalization of bioactive compounds, and will be useful for modern peptide synthesis and drug discovery.

Omega plate for the treatment of acetabular fractures involving the quadrilateral plate.

This retrospective study aimed to assess the outcome of a modified Stoppa approach using an anatomically precontoured plate for the treatment of acetabular fractures. In total, 30 patients (mean age 50.3 years; 25 men and 5 women) with acetabular fractures were treated between January 1, 2018 and December 31, 2019. In all 30 cases, fracture reduction was performed through a modified Stoppa approach and fixed with the omega plate. In specific fracture patterns, additional approaches were needed (lateral window in 4 cases and posterior Kocher-Langenbeck approach in 7 cases). Patients were assessed for restoration of the hip joint congruency, complications, and overall fracture reduction. Quality of reduction was categorized based on Matta's radiological principles and to assess functional outcome the Merle d'Aubigné-Postel and Harris hip score was used. The average anesthesia time was 253.6 min, the mean intraoperative blood lost was 266.6 ml and the mean intraoperative fluoroscopy dose was 3.21 mGy. According to Matta criteria for reduction quality, anatomical reduction was recorded in 22 cases, imperfect reduction in 6 cases and 2 cases had poor reduction. The average follow-up was 22.5 months. Malunion, loss of reduction or implant loosening were not recorded. Late complications included one case of avascular necrosis of the femoral head and post-traumatic arthritis changes in 5 cases. At the final follow-up, a mean Merle d'Aubigné-Postel score of 13.26±4.46 and a mean Harris score of 86.03±13.37 were recorded. The possibility of an anatomically precontoured plate with subsequent lower operative time combined with stable fixation of the primary acetabular fracture fragments and the quadrilateral plate makes the omega plate a viable option for treating acetabular fractures with a very low complication rate and good to excellent results in 89% of the cases.

Influence of nonstatistical properties in nuclear structure on emission of prompt fission neutrons

The Hauser-Feshbach Fission Fragment Decay (HF$^3$D) model is extended to calculate the prompt fission neutron spectrum (PFNS) for the thermal neutron induced fission on $^{235}$U, where the evaporated neutrons from all possible fission fragment pairs are aggregated. By studying model parameter sensitivities on the calculated PFNS, as well as non-statistical behavior of low-lying discrete level spin distribution, we conclude that discrepancies between the aggregation calculation and the experimental PFNS seen at higher neutron emission energies can be attributed to both the primary fission fragment yield distribution and the possible high spin states that are not predicted by the statistical theory of nuclear structure.

Estimation of fission yield and cross-section for thorium-based molten salt reactor and accelerator driven system

Thorium is the primary candidate fuel in Thorium-based Molten Salt Reactor (TMSR) and Accelerator Driven System (ADS). However, to utilize Thorium in the reactor and accelerator systems, nuclear data in the literature are not sufficient for neutron-induced fission reaction process. Therefore, we estimated neutron fission cross-section [Formula: see text] (mb), independent [Formula: see text] and primary fission fragment yield [Formula: see text], mass-dependent average neutron multiplicity [Formula: see text], energy-dependent average neutron multiplicity [Formula: see text] and neutron emission multiplicity distribution [Formula: see text] of [Formula: see text] for different neutron incident energy values, 1 MeV, 1.5 MeV, 3 MeV, 5.5 MeV, 7.7 MeV, 10 MeV, 14.8 MeV and 20 MeV, where the energy region is important for the reactor and accelerator systems used in the industry. The obtained results are compared with experimental data obtained from the literature and are discussed for each energy value.

Isomeric discrimination of kaempferol versus luteolin by online energy-resolved mass spectrometry

Isomers are widely distributed in Chinese herbal medicines,and can be discriminated by energy-resolved mass spectrometry( ER-MS). However,ER-MS was performed through direct injection of reference compounds with syringe pump,which encountered a significant technical barrier for high-throughput and automated measurements. Herein,online ER-MS was conducted using LC-MS platform,and a pair of isomers,kaempferol vs luteolin,were employed as a case study to illustrate and assess the utility of online ER-MS for isomeric discrimination. High-resolution tandem mass spectrometry data of both flavonoids were acquired on LC-QE-Orbitrap-MS,and the fragmentation pathways responsible for the primary fragment ions were proposed. The primary signal in MS1 occurred at m/z 285( [M-H]-),and the primary signals of either compound generated by retro-Diels-Alder fragmentation were observed at m/z 151 and 133. The spectral information was subsequently transferred onto LC-Qtrap-MS platform to carry out online ER-MS. Two precursor-to-product ion transition candidates were constructed as m/z 285>151 and 285>133,and either afterward derived a set of pseudo-ion transitions( PITs) and so forth,exactly corresponding to a series of progressive collision energies( eg-5,-8,-11 e V,and so on). All PITs were typed into the monitoring list of multiple reaction monitoring program to generate the peak area datasets. Either dataset was normalized using the highest values in the set and imported into Graph Pad Prism software to plot the Gaus-sian-shaped curve that was termed as the break-down graph. The apex of the regressive curve was termed as optimal collision energy( OCE). The OCE values corresponding to m/z 285>151 were calculated as-29. 06 e V and-35. 71 e V for kaempferol and luteolin,respectively. In the case of m/z 285>133,the OCEs were yielded as-44. 15 e V for kaempferol and-49. 01 e V for luteolin. With re-ference to their chemical structures,the location of hydroxyl group was regarded to be responsible for the differences of either m/z 285>151 or 285>133 between the isomers,attributing to their different bond properties. Above all,online ER-MS offers an eligible tool for isomeric discrimination,and provides meaningful information for the accurate chemical composition characterization based on LC-MS,which is not limited to Chinese herbal medicines.

Light fragment and neutron emission in high-energy proton induced spallation reactions * *Supported by the National Natural Science Foundation of China (11722546, 11675226) and the Talent Program of South China University of Technology

The dynamics of high-energy proton-induced spallation reactions on target nuclides of 56Fe, 58Ni, 107Ag, 112Cd, 184W, 181Ta, 197Au, and 208Pb are investigated with the quantum molecular dynamics transport model motivated by the China initiative Accelerator Driven System (CiADS) in Huizhou and the China Spallation Neutron Source (CSNS) in Dongguan. The production mechanism of light nuclides and fission fragments is thoroughly analyzed, and the results obtained thereby are compared with available experimental data. The statistical code GEMINI is employed in conjunction with a transport model for describing the decay of primary fragments. For the treatment of cluster emission during the preequilibrium stage, a surface coalescence model is implemented into the model. It is found that the available data in terms of total fragment yields are well reproduced in the combined approach for spallation reactions both on the heavy and light targets. The energetic light nuclides (deuteron, triton, helium isotopes etc) mainly created during the preequilibrium stage are treated within the framework of surface coalescence, whereas their evaporation is described in the conventional manner by the GEMINI code. With this combined approach, a good overall description of light clusters and neutron emission is obtained, and some discrepancies with the experimental data are discussed. Possible production of radioactive isotopes in the spallation reactions is also analyzed, i.e., the 6,8He energy spectra.

Casualty Risks Induced by Primary Fragmentation Hazards from High-explosive munitions

Fatalities and injuries are mainly attributed to primary fragmentation if accidental or malevolent detonation of high-explosive munitions occurs in an open space. This study aims to develop a simulation-based approach to assess individual casualty risks from primary fragments naturally generated by detonation of high-explosive munitions, which enables a stochastic characterization of fragment generation, trajectories, modelling uncertainties, and human vulnerability. The proposed method is demonstrated by a numerical example estimating the fatality and injury risks for an individual in a standing position exposed to the detonation of a single 105 mm projectile. The results suggest that, as expected, the individual fatality and injury risks decrease with an increasing stand-off distance. At a stand-off distance greater than 40 m, an individual is more likely to suffer injuries rather than fatality. The safety distance obtained from the present study is 97 m which is close to but less conservative than a safety distance of 104 m in existing literature and standards.

Optimizing bat bioacoustic surveys in human‐modified Neotropical landscapes

AbstractDuring the last decades, the use of bioacoustics as a non‐invasive and cost‐effective sampling method has greatly increased worldwide. For bats, acoustic surveys have long been known to complement traditional mist‐netting, however, appropriate protocol guidelines are still lacking for tropical regions. Establishing the minimum sampling effort needed to detect ecological changes in bat assemblages (e.g., activity, composition, and richness) is crucial in view of workload and project cost constraints, and because detecting such changes must be reliable enough to support effective conservation management. Using one of the most comprehensive tropical bat acoustic data sets, collected in the Amazon, we assessed the minimum survey effort required to accurately assess the completeness of assemblage inventories and habitat selection in fragmented forest landscapes for aerial insectivorous bats. We evaluated a combination of 20 different temporal sampling schemes, which differed regarding number of hours per night, number of nights per site, and sampling only during the wet or dry season, or both. This was assessed under two different landscape scenarios: in primary forest fragments embedded in a matrix of secondary forest and in the same forest fragments, but after they had been re‐isolated through clearing of the secondary forest. We found that the sampling effort required to achieve 90% inventory completeness varied considerably depending on the research aim and the landscape scenario evaluated, averaging ~80 and 10 nights before and after fragment re‐isolation, respectively. Recording for more than 4 h per night did not result in a substantial reduction in the required number of sampling nights. Regarding the effects of habitat selection, except for assemblage composition, bat responses in terms of richness, diversity, and activity were similar across all sampling schemes after fragment re‐isolation. However, before re‐isolation, a minimum of four to six sampling hours per night after dusk and three to five nights of sampling per site were needed to detect significant effects that could otherwise go unnoticed. Based on our results, we propose guidelines that will aid to optimize sampling protocols for bat acoustic surveys in the Neotropics.