Weak Extinction Research Articles

Novelty facilitates the persistence of aversive memory extinction by dopamine regulation in the hippocampus and ventral tegmental area

Aversive memory extinction comprises a novel learning that blocks retrieving a previously formed traumatic memory. In this sense, aversive memory extinction is an excellent tool for decreasing fear responses. However, this tool it's not effective in the long term because of original memory spontaneous recovery. Thus, searching for alternative strategies that strengthen extinction learning is essential. In the current study, we evaluated the effects of a novel context (i.e., novelty) exposure on aversive memory extinction enhancement over days and the dopaminergic system requirement. Given the purpose, experiments were conducted using 3-month-old male Wistar rats. Animals were trained in inhibitory avoidance (IA). Twenty-four hours later, rats were submitted to a weak extinction protocol. Still, 30 min before the first extinction session, animals were submitted to an exploration of a novel context for 5 min. After, memory retention and persistence were evaluated 24 h, 3, 7, 14, and 21 days later. The exposition of a novel context caused a decrease in aversive responses in all days analyzed and an increase in dopamine levels in the hippocampus. The intrahippocampal infusion of dopamine in the CA1 area or the stimulation of the ventral tegmental area (VTA) by a glutamatergic agonist (NMDA) showed similar effects of novelty. In contrast, VTA inhibition by a gabaergic agonist (muscimol) impaired the persistence of extinction learning induced by novelty exposition and caused a decrease in hippocampal dopamine levels. In summary, we show that novel context exposure promotes persistent aversive memory extinction, revealing the significant role of the dopaminergic system.

Autonomous and non-autonomous modified Leslie-type stochastic predator-prey model with foraging arena scheme.

This paper aims to investigate how the external random noise affects the dynamics of the predator-prey model with a modified Leslie and foraging arena scheme. The autonomous and non-autonomous systems are both considered. First, some asymptotic behaviors of two species are explored including the threshold point. Then, the existence of an invariant density is deduced, based on the theory elaborated in Pike and Luglato (1987). Moreover, the famous LaSalle-type theorem is applied to investigate weak extinction, which requires weaker parametric restrictions. A numerical study is conducted to illustrate our theory.

Detectability of biosignatures on LHS 1140 b

Context. Terrestrial extrasolar planets around low-mass stars are prime targets when searching for atmospheric biosignatures with current and near-future telescopes. The habitable-zone super-Earth LHS 1140 b could hold a hydrogen-dominated atmosphere, and is an excellent candidate for detecting atmospheric features. Aims. In this study we investigate how the instellation and planetary parameters influence the atmospheric climate, chemistry, and spectral appearance of LHS 1140 b. We study the detectability of selected molecules, in particular potential biosignatures, with the upcoming James Webb Space Telescope (JWST) and Extremely Large Telescope (ELT). Methods. In the first step we used the coupled climate–chemistry model 1D-TERRA to simulate a range of assumed atmospheric chemical compositions dominated by molecular hydrogen (H2) and carbon dioxide (CO2). In addition, we varied the concentrations of methane (CH4) by several orders of magnitude. In the second step we calculated transmission spectra of the simulated atmospheres and compared them to recent transit observations. Finally, we determined the observation time required to detect spectral bands with low-resolution spectroscopy using JWST, and the cross-correlation technique using ELT. Results. In H2-dominated and CH4-rich atmospheres oxygen (O2) has strong chemical sinks, leading to low concentrations of O2 and ozone (O3). The potential biosignatures ammonia (NH3), phosphine (PH3), chloromethane (CH3Cl), and nitrous oxide (N2O) are less sensitive to the concentration of H2, CO2, and CH4 in the atmosphere. In the simulated H2-dominated atmosphere the detection of these gases might be feasible within 20 to 100 observation hours with ELT or JWST when assuming weak extinction by hazes. Conclusions. If further observations of LHS 1140 b suggest a thin, clear, hydrogen-dominated atmosphere, the planet would be one of the best known targets to detect biosignature gases in the atmosphere of a habitable-zone rocky exoplanet with upcoming telescopes.

Optimal calculation method of aircraft infrared physical imaging simulation

In order to meet the needs of high-precision simulation images in the development process of infrared imaging detection system, the infrared physical imaging radiation transmission model for aircraft was established, and the ray tracing method was used to realize the simulation calculation of radiance image. Aiming at the difference between the reflection characteristics of the aircraft skin and the distribution characteristics of the radiation source, an optimization method for skin radiance calculation using direct lighting multi-importance sampling was proposed. Aiming at the characteristics of strong emission ability and weak extinction ability of aircraft exhaust plume, an optimization method for exhaust plume radiance calculation using combining integration was proposed. The correctness and effectiveness of the physical imaging model and calculation optimization method were verified through simulation experiments. The relative error of the skin radiation calculation is better than 0.05%, and the relative error of the tail flame radiation calculation is better than 0.1%. Compared with the traditional ray tracing method, the calculation optimization method has a faster convergence speed and stronger adaptability. Infrared imaging simulation and radiation characteristics analysis of stealth aircraft were carried out. The simulation results show that infrared stealth technology can reduce the radiation intensity in the mid-waveband and long-waveband, and increase the reflected radiation intensity in the short-waveband.

Assessment of dominating aerosol properties and their long-term trend in the Pan-Third Pole region: A study with 10-year multi-sensor measurements

Abstract The Pan-Third Pole (PTP), stretching from Eastern Asia to Middle-central Europe, has experienced unprecedented accelerated warming and even retreat of glaciers. Absorbing aerosols reduce snow and ice albedo and radiative forcing, consequently enhancing a great melting of snow cover and ice sheet in the PTP. Employing the 10-year (2007–2016) space-based active and passive measurements, this study investigated the distribution, optical properties and decadal trends for dominating aerosols at a seasonal scale in the PTP divided into six sub-regions. Results showed that the sub-regions of PTP were mainly dominated by dust, polluted dust and elevated smoke. The Taklimakan Desert (TD) and the Iranian Plateau (IP) were dominated by mineral dust, accounting for 96% and 86% of the total aerosol extinction while the Central Europe (CE), Indo-China (IC) and Anatolia Plateau (AP) were dominated by the mixture of the dominating aerosol types. The mean aerosol extinction coefficient (MAEC) showed an obvious variability depending on the sub-regions and a tendency of decreasing with an increase in the topographic height. The strongest extinction layer (>0.1 km−1) mainly occurred below 4 km and the weak extinction layers (>0.001 km−1) were mainly distributed between 5 km and 8 km, indicating pronounced vertical transport in the region. The decadal trends of columnar aerosol optical depth (AOD) showed a relation with the contributions of the dominating aerosol types. For example, significant upward or downward trends of total aerosol loading in the IC region were driven by elevated smoke while the AOD trends of total aerosol loading for the CE, the AP and the IP were driven by the dominating aerosol types. The Tibetan Plateau (TP), the cleanest region in the PTP, has been regularly exposed to polluted air masses with significant amounts of absorbing aerosols. Therefore, understanding the dominating aerosol types, properties and decadal trends in the PTP region will contribute considerably to assessing their effects on radiative forcing, climate change, and even snowmelt and glacier retreat.

Extinction mechanisms of hyperbolic h-BN nanodisk**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFA0203500), the National Natural Science Foundation of China (Grant No. 11874407), and Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB 30000000).

We applied the finite element method to calculate the extinction spectrum of single hyperbolic hexagonal boron nitride (h-BN) nanodisk. We show that the hyperbolic h-BN nanodisk exhibits two extinction mechanisms in the mid-infrared region. The volume confined phonon polaritons resonances of the nanodisk give rise to a series of weak extinction peaks. The localized surface phonon polaritons lead to a robust dipolar extinction, and the extinction peak position is tunable by varying the size of the h-BN nanodisk. These findings reveal the mechanisms of the interaction between light and resonant h-BN nanodisk, which are essential for h-BN related opto-electromagnetic applications.

Endocannabinoid modulating drugs improve anxiety but not the expression of conditioned fear in a rodent model of post-traumatic stress disorder

The endocannabinoid (eCB) system is a potential target for the treatment of symptoms of post-traumatic stress disorder (PTSD). Similar to clinical PTSD, approximately 25–30% of rats that undergo cued fear conditioning exhibit impaired extinction learning. In addition to extinction-resistant fear, these “weak extinction” (WE) rats show persistent anxiety-like behaviors. The goal of the present study was to test the hypothesis that behavioural differences between WE animals and those presenting normal extinction patterns (strong extinction; SE) could be mediated by the eCB system. Rats undergoing fear conditioning/extinction and fear recall sessions were initially segregated in weak and strong-extinction groups. Two weeks later, animals underwent a fear recall session followed by a novelty-suppressed feeding (NSF) test. In acute experiments, WE rats were injected with either the fatty acid amide hydrolase (FAAH) inhibitor URB597 or the CB1 agonist WIN55,212-2 1 h prior to long-term recall and NSF testing. SE animals were injected with the inverse CB1 receptor agonist AM251. In chronic experiments, WE and SE rats were given daily injections of URB597 or AM251 between short and long-term recall sessions. We found that acute administration of WIN55,212-2 but not URB597 reduced anxiety-like behaviour in WE rats. In contrast, AM251 was anxiogenic in SE animals. Neither treatment was effective in altering freezing expression during fear recall. The chronic administration of AM251 to SE or URB597 to WE did not alter fear or anxiety-like behaviour or changed the expression of FAAH and CB1. Together, these results suggest that systemic manipulations of the eCB system may alter anxiety-like behaviour but not the behavioural expression of an extinction-resistant associative fear memory.

The threshold of stochastic Gilpin–Ayala model subject to general Lévy jumps

This paper investigates a stochastic Gilpin–Ayala model with general Levy jumps and stochastic perturbation to around the positive equilibrium of corresponding deterministic model. Sufficient conditions for extinction are established as well as nonpersistence in the mean, weak persistence and stochastic permanence. The threshold between weak persistence and extinction is obtained. Asymptotic behavior around the positive equilibrium of corresponding deterministic model is discussed. Our results imply the general Levy jumps is propitious to population survival when its intensity is more than 0, and some changes profoundly if not. Numerical simulink graphics are introduced to support the analytical findings.

A stochastic prey-predator model with time-dependent delays

A stochastic predator-prey system with time-dependent delays is considered. Firstly, we show the existence of a global positive solution and stochastically ultimate boundedness. Secondly, the critical value between weak persistence and extinction of the prey is obtained and we also give the asymptotic pathwise estimation. Finally, we simulate the model to illustrate our results.

Extinction memory is facilitated by methylphenidate and regulated by dopamine and noradrenaline receptors

Extinction is defined as the learned inhibition of retrieval and is the mainstay of exposure therapy, which is widely used to treat drug addiction, phobias and fear disorders. The psychostimulant, methylphenidate (MPH) is known to increase extracellular levels of noradrenaline and dopamine by blocking their reuptake and studies have demonstrated that MPH can modulate hippocampal physiology and/or functions including long-term potentiation (LTP), learning and memory. However, the influence of MPH on fear extinction memory has been insufficiently studied. Here we investigate the effect of MPH infused into the CA1 region of the hippocampus on extinction memory in animals normally incapable of showing contextual fear conditioning (CFC) extinction because of weak training, and the possible mechanisms through which it acts during this process. For this, male Wistar rats with infusion cannulae stereotaxically implanted in the CA1 region were submitted to a weak extinction protocol in a CFC apparatus. Animals that received intra-CA1 infusion of MPH (12.5μg/side) 20min before the extinction training (Ext Tr) expressed less freezing behavior than Veh-treated animals during both Ext Tr and extinction retention Test (Ext Test). Additionally, the administration of MPH+Timolol (1μg/side) or MPH+SCH23390 (1.5μg/side) intra-CA1 20min before the Ext Tr blocked the enhancing effect of the MPH on extinction learning. These results suggest that MPH in the CA1 region of the hippocampus is able to induce the consolidation of extinction memory and this process occurs through both β-adrenergic and D1/D5 dopaminergic receptors.

Permanence and extinction in non-autonomous logistic system with random perturbation and feedback control

In this paper, we study a stochastic non-autonomous logistic system with feedback control. Sufficient conditions for stochastic asymptotically bounded, extinction, non-persistence in the mean, weak persistence, and persistence in the mean are established. The critical number between weak persistence and extinction is obtained. A very important fact is found in our results, that is, the feedback control is harmless to the permanence of species under the randomized environment.

Time-resolved photoisomerization of 1,1′-di-tert-butylstilbene and 1,1′-dicyanostilbene

Photoisomerization of 1,1′-di-tert-butylstilbene (3) and 1,1′-dicyanostilbene (4) is monitored with stationary and broadband transient absorption spectroscopy. The electron affinity of the substituents correlates with the shift of the absorption band. The weak extinction of 3 complicates data interpretation, but comparison with earlier measured 1,1′-dimethylstilbene (1) and 1,1′-diethylstilbene (2) helps to assign transient spectra and relaxation paths. For 3 a long-lived perpendicular state P is observed with lifetime τP=134ps in acetonitrile. For 4τP=2.1ps in acetonitrile and 27ps in n-hexane, the difference indicating a substantial dipole moment (∼3D) of the P state.

Weak extinction versus global exponential growth of total mass for superdiffusions

Consider a superdiffusion $X$ on $\mathbb R^d$ corresponding to the semilinear operator $\mathcal{A}(u)=Lu+\beta u-ku^2,$ where $L$ is a second order elliptic operator, $\beta(\cdot)$ is in the Kato class and bounded from above, and $k(\cdot)\ge 0$ is bounded on compact subsets of $\R^d$ and is positive on a set of positive Lebesgue measure. The main purpose of this paper is to complement the results obtained in \cite{Englander:2004}, in the following sense. Let $\lambda_\infty $ be the $L^\infty$-growth bound of the semigroup corresponding to the Schr\"odinger operator $L+\beta $. If $\lambda_\infty \neq0$, then we prove that, in some sense, the exponential growth/decay rate of $\|X_t\|$, the total mass of $X_t$, is $\lambda_\infty $. We also describe the limiting behavior of $\exp(-\lambda_\infty t)\|X_t\|$ in these cases. This should be compared to the result in \cite{Englander:2004}, which says that the generalized principal eigenvalue $\lambda_2$ of the operator gives the rate of {\it local} growth when it is positive, and implies local extinction otherwise. It is easy to show that $\lambda_{\infty}\ge \lambda_2$, and we discuss cases when $\lambda_{\infty}> \lambda_2$ and when $\lambda_{\infty}= \lambda_2$. When $\lambda_\infty =0$, and under some conditions on $\beta$, we give a sufficient and necessary condition for the superdiffusion $X$ to exhibit weak extinction. We show that the branching intensity $k$ affects weak extinction; this should be compared to the known result that $k$ does not affect weak {\it local} extinction (which only depends on the sign of $\lambda_2$, and which turns out to be equivalent to local extinction) of $X$.

Flurlite, Zn3Mn2+Fe3+(PO4)3(OH)2·9H2O, a new mineral from the Hagendorf Süd pegmatite, Bavaria, with a schoonerite-related structure

AbstractFlurlite, ideally Zn3Mn2+Fe3+(PO4)3(OH)2·9H2O, is a new mineral from the Hagendorf-Süd pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Flurlite occurs as ultrathin (<1 μm) translucent platelets that form characteristic twisted accordion-like aggregates. The colour varies from bright orange red to dark maroon red. Cleavage is perfect parallel to (001). The mineral occurs on mitridatite and is closely associated with plimerite. Other associated minerals are beraunite, schoonerite, parascholzite, robertsite and altered phosphophyllite. The calculated density of flurlite is 2.84 g cm–3. It is optically biaxial (–), α = 1.60(1), β= 1.65(1) and γ = 1.68(1), with weak dispersion and parallel extinction, X ≈ c, Y ≈ a, Z ≈ b. Pleochroism is weak, with colours: X = pale yellow, Y = pale orange, Z = orange brown. Electron microprobe analyses (average of seven) with FeO and Fe2O3 apportioned and H2O calculated on structural grounds, gave ZnO 25.4, MnO 5.28, MgO 0.52, FeO 7.40, Fe2O3 10.3, P2O5 27.2, H2O 23.1, total 99.2 wt.%. The empirical formula, based on 3 P a.p.f.u. is Zn2.5Mn2+0.6Fe2+0.8Mg0.1Fe3+(PO4)3(OH)2·9H2O. Flurlite is monoclinic, P21/m, with the unit-cell parameters (at 100 K) of a = 6.3710(13), b = 11.020(2), c = 13.016(3) Å, β = 99.34 (3)°. The strongest lines in the X-ray powder diffraction pattern are [dobs in Å(I) (hkl)] 12.900(100)(001); 8.375(10)(011); 6.072(14)(101); 5.567(8)(012); 4.297(21)(003); 2.763(35)(040). Flurlite (R1 = 0.057 for 995 F > 4σ(F)) has a heteropolyhedral layer structure, with layers parallel to (001) and with water molecules packing between the layers. The slab-like layers contain two types of polyhedral chains running parallel to [100]: (a) chains of edge-sharing octahedra containing predominantly Zn and (b) chains in which Fe3+-centred octahedra share their apices with dimers comprising Zn-centred trigonal bipyramids sharing an edge with PO4 tetrahedra. The two types of chains are interconnected by corner-sharing along [010]. A second type of PO4 tetrahedron connects the chains to MnO2(H2O)4 octahedra along [010] to complete the structure of the (001) slabs. Flurlite has the same stoichiometry as schoonerite, but with dominant Zn rather than Fe2+ in the edge-shared chains. Schoonerite has a similar heteropolyhedral layer structure with the same layer dimensions 6.4 × 11.1 Å. The different symmetry (orthorhombic, Pmab) for schoonerite reflects a different topology of the layers.

Palladosilicide, Pd2Si, a new mineral from the Kapalagulu Intrusion, Western Tanzania and the Bushveld Complex, South Africa

AbstractPalladosilicide, Pd2Si, is a new mineral (IMA 2014-080) discovered in chromite-rich samples from the Kapalagulu intrusion, western Tanzania (30°03′51′′E 5°53′16′′S and 30°05′37′′E 5°54′26′′S) and from the UG-2 chromitite, Bushveld complex, South Africa. A total of 13 grains of palladosilicide, ranging in size from 0.7 to 39.1 μm (equivalent circle diameters), were found. Synthetic Pd2Si is hexagonal, space groupP62m, witha= 6.496(5),c= 3.433(4) Å,V= 125.5(1) Å3,c:a= 0.529 withZ= 3. The strongest lines calculated from the powder pattern (Anderko and Schubert, 1953) are [din Å (I) (hkl)] 2.3658 100 (111); 2.1263 37 (120); 2.1808 34 (021); 3.240 20 (110); 1.8752 19 (030); 1.7265 12 (002); 1.3403 11 (122); 1.2089 10 (231). The calculated density for three analyses varies from 9.562 to 9.753 g cm–3. Palladosilicide is considered to be equivalent to synthetic Pd2Si based on results from electron backscattered diffraction analyses. Reflectance data in air for the four Commission on Ore Mineralogy wavelengths are [λ nm,R1(%)R2(%)] 470 49.6 52.7; 546 51.2 53.8; 589 51.6 53.7; 650 51.7 53.3 and the mineral is bright creamy white against chromite, weakly bireflectant and displays no discernible pleochroism or twinning. It is weakly anisotropic, has weak extinction and rotation tints in shades of blue and olive green. Electron probe microanalyses of palladosilicide yield a simplified formula of Pd2Si.

Dynamics of a General Stochastic Nonautonomous Lotka-Volterra Model with Delays and Impulsive Perturbations

A stochastic nonautonomous N-species Lotka-Volterra model with delays and impulsive perturbations is investigated. For this model, sufficient conditions for extinction, nonpersistence in the mean, weak persistence and stochastic permanence are given, respectively. The influences of the stochastic noises, and the impulsive perturbations on the properties of the stochastic model are also discussed. The critical value between weak persistence and extinction is obtained. Finally, numerical simulations are given to support the theoretical analysis results.

Towards a better preclinical model of PTSD: Characterizing animals with weak extinction, maladaptive stress responses and low plasma corticosterone

Most of the available preclinical models of PTSD have focused on isolated behavioural aspects and have not considered individual variations in response to stress. We employed behavioural criteria to identify and characterize a subpopulation of rats that present several features analogous to PTSD-like states after exposure to classical fear conditioning. Outbred Sprague-Dawley rats were segregated into weak- and strong-extinction groups on the basis of behavioural scores during extinction of conditioned fear responses. Animals were subsequently tested for anxiety-like behaviour in the open-field test (OFT), novelty supressed feeding (NSF) and elevated plus maze (EPM). Baseline plasma corticosterone was measured prior to any behavioural manipulation. In a second experiment, rats underwent OFT, NSF and EPM prior to being subjected to fear conditioning to ascertain whether or not pre-stress levels of anxiety-like behaviours could predict extinction scores. We found that 25% of rats exhibit low extinction rates of conditioned fear, a feature that was associated with increased anxiety-like behaviour across multiple tests in comparison to rats showing strong extinction. In addition, weak-extinction animals showed low levels of corticosterone prior to fear conditioning, a variable that seemed to predict extinction recall scores. In a separate experiment, anxiety measures taken prior to fear conditioning were not predictive of a weak-extinction phenotype, suggesting that weak-extinction animals do not show detectable traits of anxiety in the absence of a stressful experience. These findings suggest that extinction impairment may be used to identify stress-vulnerable rats, thus providing a useful model for elucidating mechanisms and investigating potential treatments for PTSD.

Persistence and extinction of a stochastic Gilpin-Ayala model with jumps

This paper considers a stochastic Gilpin–Ayala model with jumps. First, we show the model that has a unique global positive solution. Then we establish the sufficient conditions for extinction, nonpersistence in the mean, weak persistence, and stochastic permanence of the solution. The threshold between weak persistence and extinction is obtained. Finally, we make simulations to conform our analytical results. The results show that the jump process can change the properties of the population model significantly. Copyright © 2014 John Wiley & Sons, Ltd.

Effects of the substitution of P2O5 by B2O3 on the structure and dielectric properties in (90−x) P2O5–xB2O3–10Fe2O3 glasses

90%[xB2O3 (1−x) P2O5] 10%Fe2O3, glass systems where (x=0mol%, 5mol%, 10mol%, 15mol%, 20mol%) was prepared via a melt quenching technique. The structure of glass is investigated at room temperature by, Raman and EPR spectroscopy. Raman studies have been performed on these glasses to examine the distribution of different borate and phosphate structural groups.We have noted an increase from 3 to 4 in the coordination number of the boron atoms from 3 to 4, i.e., the conversion of the BO3 triangular structural units into BO4 tetrahedra.The samples have been investigated by means of electron paramagnetic resonance (EPR). The results obtained from the gef=4.28 EPR line are typical of the occurrence of iron (III) occupying substitutional sites.Moreover, the dielectric sizes such as ε′(ω), ε″(ω), imaginary parts of the electrical modulus, M*(ω) and the loss tanδ, their variation with frequency at room temperature show a decrease in relaxation intensity with an increase in the concentration of (B2O3). On the present work, we have found a weak extinction index with our new glass.

The threshold between permanence and extinction for a stochastic Logistic model with regime switching

A stochastic logistic model under regime switching is proposed and investigated. Sufficient conditions for extinction, non-persistence in the mean, weak persistence and stochastic permanence are established. The threshold between weak persistence and extinction is obtained. Then we show that this threshold also is the threshold between stochastic permanence and extinction under a simple additional condition. The results show that firstly, the stationary probability distribution of the Markov chain plays a key role in determining the permanence and extinction of the population. Secondly, different types of environmental noises have different effects on the permanence and extinction of the population. Thirdly, the more the stochastic noises, the easier the population goes to extinction.