bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of fire on ant assemblages does not depend on habitat openness but does select for large, gracile predators
Authors: Bishop Tom R. , Tomlinson Andy , McNeice Travers , Sfenthourakis Spyros , Parr Catherine L. 
Published: June 2021

AbstractEcosystems can respond in a variety of ways to the same agent of disturbance. In some contexts, fire causes large and long‐lasting changes to ecological communities. In others, fire has a limited or short‐lived impact on assemblages of animals and plants. Understanding why this occurs is critical if we are to manage these kinds of disturbances across the globe. A recent synthesis proposed that these seemingly idiosyncratic responses to fire can be understood in the context of habitat openness pre‐disturbance. Assemblages in open habitats should respond less to a single fire event that those in closed habitats. We provide a test of this hypothesis by examining the response of ant (Hymenoptera: Formicidae) communities to large‐scale fire events in three habitats of different natural canopy openness on the Peloponnese peninsula in Greece. We also test the hypothesis that assemblage responses to fire are trait dependent. Fire simplifies the physical structure of the environment, increases insolation, and limits opportunities for ants to exploit herbivorous feeding strategies. Consequently, we predict that ants will face a strong environmental filter between unburnt and recently burnt plots, which will be reflected in their functional morphology. Our analysis shows that burnt plots have more individual ants, more species and an almost complete compositional change relative to unburnt plots. These changes do not depend on initial canopy openness. Rather, we suggest that openness must be interpreted relative to the study taxon; for ants, openness should be measured closer to the ground level. In our study, ground‐level openness does not vary across the plots, which may explain the results. Furthermore, ants in burnt plots are significantly larger, have relatively longer legs, relatively longer mandibles, and more elongate heads. This morphotype fits with our prediction of ants that can move and feed successfully in the burnt micro‐landscape. Ultimately, more work is needed to fully explore the relationship between habitat openness and the response to fire. Our results showing a filtered set of ant morphologies in burnt environments suggest that ant traits may offer a further way forward to understand the faunal response to fire and disturbance in general.
Analyzing long‐term water quality of lakes in Rhode Island and the northeastern United States with an anomaly approach
Authors: Hollister J. W. , Kellogg D. Q. , Kreakie B. J. , Shivers S. D. , Milstead W. B. , Herron E. M. , Green L. T. , Gold A. J. 
Published: June 2021

AbstractAddressing anthropogenic impacts on aquatic ecosystems is a focus of lake management. Controlling phosphorus and nitrogen can mitigate these impacts, but determining management effectiveness requires long‐term datasets. Recent analysis of the LAke multi‐scaled GeOSpatial and temporal database for the Northeast (LAGOS‐NE) United States found stable water quality in the northeastern and midwestern United States; however, sub‐regional trends may be obscured. We used the University of Rhode Island’s Watershed Watch Volunteer Monitoring Program (URIWW) dataset to determine if there were sub‐regional (i.e., 3000 km2) water quality trends. URIWW has collected water quality data on Rhode Island lakes and reservoirs for over 25 yr. The LAGOS‐NE and URIWW datasets allowed for comparison of water quality trends at regional and sub‐regional scales, respectively. We assessed regional (LAGOS‐NE) and sub‐regional (URIWW) trends with yearly median anomalies calculated on a per‐station basis. Sub‐regionally, temperature and chlorophyllaincreased from 1993 to 2016. Total nitrogen, total phosphorus, and the nitrogen:phosphorus ratio (N:P) were stable. At the regional scale, the LAGOS‐NE dataset showed similar trends to prior studies of the LAGOS‐NE with chlorophylla, total nitrogen, and N:P all stable over time. Total phosphorus did show a very slight increase. In short, algal biomass, as measured by chlorophyllain Rhode Island lakes and reservoirs increased, despite stability in total nitrogen, total phosphorus, and the nitrogen to phosphorus ratio. Additionally, we demonstrated both the value of long‐term monitoring programs, like URIWW, for identifying trends in environmental condition, and the utility of site‐specific anomalies for analyzing for long‐term water quality trends.
Iron/2,6‐Di(pyrazol‐1‐yl)pyridine Complexes with a Discotic Pattern of Alkyl or Alkynyl Substituents
Authors: Galadzhun Iurii , Kulmaczewski Rafal , Cespedes Oscar , Halcrow Malcolm A. 
Published: June 2021

Abstract2,6‐Di(4‐iodopyrazol‐1‐yl)pyridine is converted to 2,6‐di(4‐{alkyn‐1‐yl}pyrazol‐1‐yl)pyridine (L1R; R’=CnH2n−3, n=12, 14, 16) derivatives by Sonogashira reactions. Hydrogenation of these intermediates yields the corresponding 2,6‐di(4‐alkylpyrazol‐1‐yl)pyridine (L2R; R=CnH2n+1) derivatives. Homoleptic Fe[BF4]2 complexes of all these ligands were prepared, bearing four long chain substituents in a discotic‐type array. Crystallographic data from two L1R ligands imply the alkynyl substituents do not undergo intermolecular interdigitation in the solid state, which could explain the lower crystallinity and ill‐defined spin‐crossover in their iron complexes. Solid [Fe(L2R)2][BF4]2 (n=12 and 14) exhibit an irreversible, abrupt low→high‐spin event near 350 K, which is not associated with solvent loss and may involve disordering of their alkyl chain conformations. No mesophase behavior was observed from any of these compounds.
Organocatalytic Desymmetrization of Meso‐Aziridines Via Asymmetric Intramolecular Rearrangement
Authors: Costanzo Martina , Cortigiani Mauro , Gillick‐Healy Malachi W. , Kelly Brian G. , Monasterolo Claudio , Adamo Mauro F. A. 
Published: June 2021

AbstractHerein we report the first organocatalytic method for the desymmetrization of meso‐aziridines that does not require the use of an external nucleophilic reagent. The process was designed upon a base promoted rearrangement of bicyclic meso‐cyclopentanone aziridines, that progresses in intramolecular fashion to provide densely functionalized cyclic ketones, key intermediates for the preparation of Active Pharmaceutical Ingredients. The key enantio‐determining step proceeded under the catalysis of a bifunctional thiourea organocatalyst. The process provides an entry to a class of highly functionalized chiral amines, 4‐aminocyclopentenones, not accessible with previous desymmetrization methods. The ambiphilic nature of the products makes them versatile synthetic intermediates in the preparation of natural products and popular antiviral nucleoside inhibitors, for example abacavir.
A Highly Congested Dioxapyrenophane from an Attempted Synthesis of the Highly‐Strained 1,1,6,6‐Tetramethyl[6](2,11)teropyrenophane
Authors: Ghods Ghasemabadi Parisa , Zhao Yuming , Bodwell Graham J. 
Published: June 2021

AbstractSynthetic studies aimed at the synthesis of 1,1,6,6‐tetramethyl[6](2,11)teropyrenophane (3 a) led to the synthesis of the structurally unusual dioxa[6.3.3](7,1,3)pyrenophane 29. The strategic approach to access 3 a resembled the one that was successfully applied in the synthesis of the higher homologues 3 b‐e, but had a key difference: three‐atom bridges were utilized instead of two‐atom bridges in the construction of the intermediate pyrenophanes which were slated to serve as precursors to access 3 a. After stepwise approaches to construct the bridges failed, it was found that two ether bridges could be installed easily in the same reaction to afford dioxa[6.3.3](7,1,3)pyrenophane 29. Considerable steric congestion around the dioxa[3.3]metacyclophane substructure arises from the presence of a methyl group on each of the benzylic positions of the three‐atom bridges. Although the conversion of 29 into a [6](2,11)teropyrenophane was unsuccessful, the finding that ether bridges in this structurally uncommon dioxacyclophane could be formed easily offers new opportunities for the synthesis of related cyclophanes that may ultimately serve as viable precursors for the synthesis of [n](2,11)teropyrenophanes.
Di‐ and Trifluorinated 2‐Azidobenzimidazole Derivatives: Synthesis, Photooxygenation, and 19F NMR Prediction
Authors: Kanitz Nils E. , Fresia Marvin , Jones Peter G. , Lindel Thomas 
Published: June 2021

AbstractThe photoreactivity of a series of hitherto unknown, multiply fluorinated 2‐azidobenzimidazole derivatives was investigated. The synthesis of the starting material includes regioselective p‐defluorination of nitrobenzene derivatives employing Ogoshi's conditions. If the 6‐position was unsubstituted, irradiation in the presence of N‐protected amino acids at 300 nm (Rayonet) led to the formation of arylesters by oxygenation of the 6‐position in good to excellent yields and perfect regioselectivity. We did not observe any displacement of fluoride. If the 6‐position itself was fluorinated, alternative positions of the benzene portion were attacked. Mechanistically, the reaction proceeds through ring opening of the singlet nitrene to the cyanodiimine or via the iminobenzimidazolium ion. The availability of a set of fluorinated photo‐adducts prompted the quantum chemical calculation of their 19F NMR chemical shifts. Even with the most suitable method investigated (ωB97XD/TApr‐cc‐pVDZ), deviations of up to 5 ppm from the experimental values were observed, underlining the importance of experimental measurements.
Quinoline‐Based Silylium Ions: Synthesis, Structure and Lewis Acidity
Authors: Kumar Nivesh , Laye Claire , Robert Frédéric , Landais Yannick 
Published: June 2021

AbstractHeteroarylsilyl cations elaborated from a quinoline skeleton have been prepared from the corresponding silanes, and their structures were studied by 1H, 29Si, and 15N NMR. DOSY experiments and DFT calculations were also carried out which showed that the silyl cation center is stabilized intramolecularly by the quinoline nitrogen atom (N1), forming a highly strained and quasi planar 4‐membered ring. Oxygenated and nitrogenated substituents at the C4 position on the quinoline ring were shown to reinforce the Si−N1 interaction through a p‐π conjugation. The Lewis acidity of this class of silylium was finally determined using Müller's nitrilium method.
Harvesting energy from high‐frequency impinging water droplets by a droplet‐based electricity generator
Authors: Wang Lili , Song Yuxin , Xu Wanghuai , Li Wanbo , Jin Yuankai , Gao Shouwei , Yang Siyan , Wu Chenyang , Wang Steven , Wang Zuankai 
Published: June 2021

AbstractHarvesting energy from water, in the form of raindrops, river, and ocean waves, is of considerable importance and has potential applications in self‐powered electronic devices and large‐scale energy needs. Recently, the droplet‐based electricity generator has shown an increase by several orders of magnitude in electrical output, overcoming the drawback of traditional droplet‐based device limited by interfacial effects. Despite this exciting result, the output performance of this novel droplet‐based electricity generator is limited by relatively low frequency of impinging droplets owing to the formation of a continuous liquid film at high impact frequency, which might hinder its practical applications. To overcome this challenge, here, we report the design of a superhydrophobic surface based droplet electricity generator, referred to as SHS‐DEG, which can timely shed water droplets from the surface without the formation of liquid film at high impact frequency, and thereby generating enhanced average electrical output. Moreover, our SHS‐DEG exhibits many distinctive advantages over conventional design including robustness, long‐term durability, and power generation stability even in harsh environments. We envision that the ability to harvest electrical energy from water droplets at high impact frequency has promising applications in various energy‐harvesting systems.image
A liquid‐solid model to optimize the application of friction reducers for hydraulic fracturing/cutting in the underground coal mine
Authors: Xiong Wei , Shen Kai , Ba Quanbin , Liu Yanbao , Zhou Houquan 
Published: June 2021

AbstractFriction reducers are widely applied to reduce friction losses in the natural oil and gas industry. The application of hydraulic fracturing in underground coal mines results in a new issue for friction reducers: The hydraulic fluid, mixed with a friction reducer, should reduce friction loss to maintain the hydraulic pressure while simultaneously discharging coal particles to clean the borehole. Most previous studies have focused on the former aspect, ignoring the discharge capacity of coal particles. To compensate for this shortcoming, a coupled flow model of coal particles and hydraulic fluid is proposed considering the interactions between the two phases and characteristics of the coal particles. The model was implemented and solved using the finite element method approach (COMSOL Multiphysics), and the impact of the injection velocity, hydraulic fluid viscosity, and stacking angle of coal particles was investigated. Before simulation, an experiment was conducted to determine the viscosity range and velocity dependency of the hydraulic fluid with a flow‐loop instrument. A field application was conducted based on simulation results. The viscosity of 2.5 mPa s is a critical value around which the maximum friction reduction efficiency can be achieved, and the discharge capacity of coal particles can be enhanced significantly above this value. The applications of hydraulic fracturing or hydraulic cutting should be coupled with the viscosity of the hydraulic fluid. The injection velocity should be sufficiently high, and the time interval of the water spray should be sufficiently large for the low‐viscosity hydraulic fluid. The stacking angle of the coal particles has little influence on the long‐term discharge process. An upward borehole is recommended for the consideration of coal particle discharge because of the gravity effect. This work provides constructive suggestions and guidance for underground hydraulic fracturing and hydraulic cutting.
Fmrp regulates oligodendrocyte lineage cell specification and differentiation
Authors: Doll Caleb A. , Scott Kayt , Appel Bruce 
Published: June 2021

AbstractNeurodevelopment requires the precise integration of a wide variety of neuronal and glial cell types. During early embryonic development, motor neurons and then oligodendrocyte precursor cells (OPCs) are specified from neural progenitors residing in the periventricular pMN progenitor domain of the spinal cord. Following gliogenesis, OPCs can differentiate as oligodendrocytes (OLs)—the myelinating glial cells of the central nervous system—or remain as OPCs. To generate unique cell types capable of highly divergent functions, these specification and differentiation events require specialized gene expression programs. RNA binding proteins (RBPs) regulate mRNA localization and translation in the developing nervous system and are linked to many neurodevelopmental disorders. One example is Fragile X syndrome (FXS), caused by the loss of the RBP fragile X mental retardation protein (FMRP). Importantly, infants with FXS have reduced white matter and we previously showed that zebrafish Fmrp is autonomously required in OLs to promote myelin sheath growth. We now find that Fmrp regulates cell specification in pMN progenitor cells such that fmr1 mutant zebrafish generate fewer motor neurons and excess OPCs. Fmrp subsequently promotes differentiation of OPCs, leading to fewer differentiating OLs in the developing spinal cord of fmr1 larvae. Although the early patterning of spinal progenitor domains appears largely normal in fmr1 mutants during early embryogenesis, Shh signaling is greatly diminished. Taken together, these results suggest cell stage‐specific requirements for Fmrp in the specification and differentiation of oligodendrocyte lineage cells.
Function–structure coupling: White matter functional magnetic resonance imaging hyper‐activation associates with structural integrity reductions in schizophrenia
Authors: Jiang Yuchao , Duan Mingjun , Li Xiangkui , Huang Huan , Zhao Guocheng , Li Xuan , Li Shicai , Song Xufeng , He Hui , Yao Dezhong , Luo Cheng 
Published: June 2021

AbstractWhite matter (WM) microstructure deficit may be an underlying factor in the brain dysconnectivity hypothesis of schizophrenia using diffusion tensor imaging (DTI). However, WM dysfunction is unclear in schizophrenia. This study aimed to investigate the association between structural deficits and functional disturbances in major WM tracts in schizophrenia. Using functional magnetic resonance imaging (fMRI) and DTI, we developed the skeleton‐based WM functional analysis, which could achieve voxel‐wise function–structure coupling by projecting the fMRI signals onto a skeleton in WM. We measured the fractional anisotropy (FA) and WM low‐frequency oscillation (LFO) and their couplings in 93 schizophrenia patients and 122 healthy controls (HCs). An independent open database (62 schizophrenia patients and 71 HCs) was used to test the reproducibility. Finally, associations between WM LFO and five behaviour assessment categories (cognition, emotion, motor, personality and sensory) were examined. This study revealed a reversed pattern of structure and function in frontotemporal tracts, as follows. (a) WM hyper‐LFO was associated with reduced FA in schizophrenia. (b) The function–structure association was positive in HCs but negative in schizophrenia patients. Furthermore, function–structure dissociation was exacerbated by long illness duration and severe negative symptoms. (c) WM activations were significantly related to cognition and emotion. This study indicated function–structure dys‐coupling, with higher LFO and reduced structural integration in frontotemporal WM, which may reflect a potential mechanism in WM neuropathologic processing of schizophrenia.
Placenta‐specific protein 1 promotes cell proliferation via the AKT/GSK‐3β/cyclin D1 signaling pathway in gastric cancer
Authors: Liu Dongyang , Shi Ke , Fu Mingshi , Chen Feng 
Published: June 2021

AbstractGastric cancer is a malignant tumor with a poor prognosis. Therefore, it is important to search for molecules that play a vital role in the development, diagnosis, and treatment of this disease. Placenta‐specific 1 (PLAC1) is one of the cancer‐testis antigens; it plays an important role in both placental development and tumorigenesis. However, the role of PLAC1 in gastric cancer has not been fully investigated, and its underlying mechanism needs further study. We first explored the expression and clinical relevance of PLAC1 in gastric cancer and performed gene set enrichment analysis of PLAC1‐related genes using online databases. Subsequently, we studied the function and mechanism of PLAC1 in gastric cancer cells through in vitro experiments. Our results showed that PLAC1 is highly expressed in gastric cancer, is associated with poor prognosis, and can promote gastric cancer cell proliferation through the AKT/GSK‐3β/cyclin D1 signaling pathway. Moreover, we discovered that AKTi attenuates the effect of PLAC1. Our study further revealed the role and mechanism of PLAC1 in gastric cancer and suggested that this antigen might be a useful molecular marker for gastric cancer diagnosis, prognosis, and treatment.
Exploring the molecular basis of UG‐rich RNA recognition by the human splicing factor TDP‐43 using molecular dynamics simulation and free energy calculation
Authors: Sun Han , Chen Wei , Chen Lin , Zheng Wenqing 
Published: June 2021

AbstractTransactivation response element RNA/DNA‐binding protein 43 (TDP‐43) is involved in the regulation of alternative splicing of human neurodegenerative disease‐related genes through binding to long UG‐rich RNA sequences. Mutations in TDP‐43, most in the homeodomain, cause neurological disorders such as amyotrophic lateral sclerosis and fronto temporal lobar degeneration. Several mutants destabilize the structure and disrupt RNA‐binding activity. The biological functions of these mutants have been characterized, but the structural basis behind the loss of RNA‐binding activity is unclear. Focused on the specific TDP‐43‐ssRNA complex (PDB code 4BS2), we applied molecular dynamics simulations and the molecular mechanics Poisson‐Boltzmann surface area free energy calculation to characterize and explore the structural and dynamic effects between ssRNA and TDP‐43. The energetic analysis indicated that the intermolecular van der Waals interaction and nonpolar solvation energy play an important role in the binding process of TDP‐43 and ssRNA. Compared with the wild‐type TDP‐43, the reduction of the polar or non‐polar interaction between all the mutants F149A, D105A/S254A, R171A/D174A, F147L/F149L/F229L/F231L and ssRNA is the main reason for the reduction of its binding free energy. Decomposing energies suggested that the extensive interactions between TDP‐43 and the nitrogenous bases of ssRNA are responsible for the specific ssRNA recognition by TDP‐43. These results elucidated the TDP‐43‐ssRNA interaction comprehensively and further extended our understanding of the previous experimental data. The uncovering of TDP‐43‐ssRNA recognition mechanism will provide us useful insights and new chances for the development of anti‐neurodegenerative drugs.
Development of a voltammetric method for the determination of rapamycin in pharmaceutical samples at pretreated pencil graphite electrode
Authors: Karaboduk Kuddusi 
Published: June 2021

AbstractThis paper describes an electroanalytical method for the determination of rapamycin using a pretreated pencil graphite electrode (P‐PGE) by differential pulse voltammetry. The electrodes were successfully characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, and Fourier transform infrared. The influences of instrumental and chemical parameters were investigated and optimized for the determination of rapamycin. Oxidation peak current obtained for rapamycin at P‐PGE was 10.5 times higher than that obtained for PGE. In pH = 3.0 H3PO4, a well‐defined irreversible anodic peak occurred at 1.07 V, which was attributed to the electro‐oxidation of rapamycin at P‐PGE. Under optimized conditions, the oxidation peak current of rapamycin was linear with its concentration in the range of 0.01–250 μmol/L, and the detection limit was 0.0075 μmol/L (S/N = 3). Also, the P‐PGE exhibited good reproducibility (relative SD [RSD] = 2.17% for 10 electrodes at different times using the same procedure), repeatability (RSD = 2.09% for 10 measurements with same electrode), and stability (95.80% for 10 days). The P‐PGE was simple to prepare and the method was successfully applied for the determination of rapamycin in spiked and real samples. In addition, for comparison, high‐performance liquid chromatographic method with ultraviolet (UV) detector was used for the determination of rapamycin.