搜索到9020篇“ EXTINCTION“的相关文章
A Speculation: Avian Migration and the K-T Extinction
2024年
One caveat to the dinosaur’s extinction is the conclusion that avian dinosaurs survived and became ancestors of birds. Their mobility enabled them to migrate great distances and find the nutrients needed to survive. Given this scenario, could the current observable migration of birds (the “dinosaurian offspring”) now be related? Migration is the regular seasonal movement undertaken by many species of birds, with the most common pattern, flying north in the Northern spring to breed in the temperate or Arctic summer and returning in the Northern autumn to wintering grounds in warmer regions of the south. The primary motivation for migration appears to be food. None of the major North-South migratory pathways fly over the Caribbean but three main fly ways, past to the west of the theorized K-T impact centre. Due to their ability to fly, the “avian Dinosaurs” adapted and survived very quickly in response to the disaster that marked the K-T boundary. It is an interesting speculation that the avian migration that we witness today is rooted in an event that occurred 66 million years ago! But it does explain why the migratory birds mostly fly from Polar summer to polar summer when they could just be as easily fly from Polar zone to the warmer equatorial region and back. In the recent article in Nature by Melanie During about identifying the late spring timing of the “Astro disaster”, it can be cited as consistent with my speculation. A late April early May Impact as suggested by During would have seen these migrations completely. The western migratory routes would have been found to be “luxurious” in vegetation in that first northern autumn after the “Astro-impact” while all eastern routes would have still been barren.
Laurence Stephenson
Stochastic Model of Dengue: Analysing the Probability of Extinction and LLN
2024年
In this article, we develop and analyze a continuous-time Markov chain (CTMC) model to study the resurgence of dengue. We also explore the large population asymptotic behavior of probabilistic model of dengue using the law of large numbers (LLN). Initially, we calculate and estimate the probabilities of dengue extinction and major outbreak occurrence using multi-type Galton-Watson branching processes. Subsequently, we apply the LLN to examine the convergence of the stochastic model towards the deterministic model. Finally, theoretical numerical simulations are conducted exploration to validate our findings. Under identical conditions, our numerical results demonstrate that dengue could vanish in the stochastic model while persisting in the deterministic model. The highlighting of the law of large numbers through numerical simulations indicates from what population size a deterministic model should be considered preferable.
Ragnimwendé SawadogoFourtoua Victorien KonanéWahabo Baguian
提取暴露时长对恐惧记忆再巩固与消退的调控
2024年
基于记忆再巩固的提取消退范式与传统消退范式在操作层面上存在很大的相似性,提取阶段一些细微的操作设置均有可能无法使记忆进入再巩固,失去持久抑制恐惧复发的效果。研究发现提取暴露时长会调控记忆进入不同的阶段,其作用机制与提取引发的预期错误量有关。本研究采用控制提取试次的数量改变提取暴露时长,在传统消退范式的基础上进行提取消退范式转化,探究提取暴露时长对记忆再巩固与消退的调控作用,并尝试用量化预期错误的方式厘清其调控机制。结果发现,单次提取消退触发记忆再巩固更新、双次提取消退无效(结果与传统消退一致)、四次提取消退增强消退记忆强度,预期错误量化结果佐证了这几个过程的差异。研究结果有利于进一步揭示人类恐惧记忆再巩固与消退的调控因素。
陈伟姚霖倪晓冰李俊娇吴子悠郑希付
Respiratory protein-driven selectivity during the Permian-Triassic mass extinction
2024年
Extinction selectivity determines the direction of macroevolution,especially during mass extinction;however,its driving mechanisms remain poorly understood.By investigating the physiological selectivity of marine animals during the Permian-Triassic mass extinction,we found that marine clades with lower O2-carrying capacity hemerythrin proteins and those relying on O2 diffusion experienced significantly greater extinction intensity and body-size reduction than those with higher O2-carrying capacity hemoglobin or hemocyanin proteins.Our findings suggest that animals with high O2-carrying capacity obtained the necessary O2 even under hypoxia and compensated for the increased energy requirements caused by ocean acidification,which enabled their survival during the Permian-Triassic mass extinction.Thus,high O2-carrying capacity may have been crucial for the transition from the Paleozoic to the Modern Evolutionary Fauna.
Haijun SongYuyang WuXu DaiJacopo Dal CorsoFengyu WangYan FengDaoliang ChuLi TianHuyue SongWilliam JFoster
关键词:EXTINCTIONSELECTIVITY
抑制高压直流系统后续换相失败的定关断角控制改进方法
2024年
定关断角控制是高压直流输电系统抑制换相失败的主要控制策略之一,但当前针对其实测型和预测型控制的研究仍未能有效解决其响应速度与控制精度不足的问题,因此提出了抑制后续换相失败的关断角控制改进方法。首先,基于对直流系统换相过程及影响因素的分析,提出了考虑电压谐波的关断角预测方法。然后,将后续换相过程的关断角预测值引入直流系统的原有控制逻辑,从而改进定关断角控制策略。最后,基于PSCAD/EMTDC对改进后的控制方法进行了仿真分析和验证。仿真结果验证了该方法能有效地抑制直流系统的后续换相失败,提升了定关断角控制的响应速度和控制精度。
李宽黄强吕学宾李晨昊郑晨一李周
关键词:高压直流输电换相失败电压谐波
Selective extinction and habitat nestedness are the main drivers of lizard nestedness in the Zhoushan Archipelago被引量:1
2024年
Nested subset pattern(nestedness)is an important part of the theoretical framework of island biogeography and community ecology.However,most previous studies often used nestedness metrics or randomization algorithms that are vulnerable to type I error.In this study,we inves-tigated the nestedness of lizard assemblages on 37 islands in the Zhoushan Archipelago,China.We used the line-transect method to survey species occurrence,abundance,and habitat types of lizards on 37 islands during 2 breeding seasons in 2021 and 2022.We applied the nested metric WNODF and the conservative rc null model to control for type I error and quantify the significance of nestedness.Spearman rank cor relations were used to evaluate the role of 4 habitat variables(island area,2 isolation indices,and habitat diversity)and 4 ecological traits(body size,geographic range size,clutch size,and minimum area requirement)in generating nestedness.The results of WNODF analyses showed that lizard assemblages were significantly nested.The habitat-by-site matrix estimated by the program NODF was also significantly nested,support-ing the habitat nestedness hypothesis.The nestedness of lizard assemblages were significantly correlated with island area,habitat diversity.clutch size,and minimum area requirement.Overall,our results suggest that selective extinction and habitat nestedness were the main drivers of lizard nestedness in our system.In contrast,the nestedness of lizard assemblages was not due to passive sampling or selective colonization.To maximize the number of species preserved,our results indicate that we should protect both large islands with diverse habitats and species with largearea requirement and clutch size.
Minchu ZhangChaonan TangQing ZhangChengxiu ZhanChuanwu ChenYanping Wang
关键词:LIZARDSNESTEDNESS
Extinction of Light in the Galactic Halo: First Observational Evidence of the Interaction of Light and Dark Matter
2024年
We study the distribution of quasars on the celestial sphere according to ground-based SDSS and space-based WISE and Gaia observations. All distributions as a function of galactic latitude, b, exhibit a decrease in quasar frequency well outside the dust in and near the galactic plane. We prove that the observed decrease in quasar frequency at high galactic latitudes is not accompanied by reddening, meaning that it can not be caused by dust. The scattering of light by the circumgalactic gas is negligible because the Thomson scattering cross section is very small. We conclude the observed scattering of light must be caused by dark matter in the galactic halo. We determine the mass and charge of dark matter particles. If the dark matter particle is a fermion its mass, mDMand charge eDM=δe, where e is the elementary charge are: mDM=3.2×10−2eV and δ=3.856×10−5. If however the dark matter particle is spinless then: mDM=0.511eV and δ=2.132×10−4. These values for the charge of a dark matter particle are orders of magnitude higher than the upper limit of the neutrino charge according to laboratory experiments. Consequently, dark matter particles are not charged neutrinos. Since dark matter particles are charged, they must emit and absorb electromagnetic radiation. However, PDM~δ2, or: PDM~1.487×10−9Pe, where Peis the power output of a single electron.
Charles H. McGruder III
Galvanic Skin Response—Extinction Biofeedback Training for Psychogenic Abdominal Pain: A Validation Protocol
2024年
Abdominal and pelvic pain of psychogenic origin is a widespread, disabling, difficult to identify, and often inadequately treated medical condition. This condition is often associated with poor quality of life due to high pain interference with daily activities. Cognitive behavioral psychological therapy and neuromodulation with biofeedback are validated therapies for the treatment of this condition. Aim of the present research work is the validation of a therapeutic protocol that involves the use of both techniques in combination. 20 patients diagnosed with psychogenic abdominal pain, of both sexes, aged between 18 and 60 years who had not benefited from pharmacological therapies were enrolled. 10 patients were randomly assigned to the control group (psychological treatment only), another 10 patients were assigned to the study group (neuromodulation with biofeedback-Galvanic skin response-extinction in combination with psychological therapy). For both groups, the pain score, interference of pain with daily living activities, pain relief, and the share of anxiety associated with the pain condition were evaluated (pre- and post-treatment). The patients who underwent the combined treatment achieved statistically significant better scores than patients in the control group, respectively −4.9 ± 0.9 vs −1.0 ± 0.4 for Pain;−5.1 ± 1.1 vs −0.9 ± 0.3 for Interference with life;−7.2 ± 3.7 vs −2.2 ± 2.1 for HAMA;4.6 ± 1.2 vs 1.1 ± 0.6 for Relief.
Maddalena CastellettiEnrico BernéErasmo Dionigio Carlo CastagnoliAlberto MontagnaGiorgio Tonon
Specialized springtail predation by Loricera beetles: An example of evolutionary stasis across the K-Pg extinction
2024年
Dear Editor,The Cretaceous-Paleogene(K-Pg)mass extinction precipitated one of the most profound restructurings of biodiversity in recent geological history.Despite the extinction of many iconic groups,particularly the non-avian dinosaurs,there is emerging evidence that previously overlooked taxa experienced stark morphological and evolutionary stasis.In this study,we report both adult and larva of beetles of the genus Loricera preserved in mid-Cretaceous Kachin amber(Figure 1),which display striking similarity to extant congeners,indicating a stasis of their specialized feeding behavior persisting at least 100 million years.
Yan-Da LiErik TihelkaMichael SEngelDiying HuangChenyang Cai
关键词:EXTINCTIONCRETACEOUS
生物材料消光特性研究进展
2024年
生物材料作为一种有别于传统无机消光材料的新型烟幕介质,悬浮于空气中,以烟幕的形式存在,通过对光的吸收和散射作用改变光波的传输特性。本文根据生物材料的复折射率特点,介绍了生物材料的吸收和散射特性,概括了生物材料单粒子、单分散凝聚粒子和多分散凝聚粒子的消光特性的表征方式,分析了影响生物材料消光特性的因素,总结了生物材料消光性能的测试方法。最后,本文提出了生物材料在复杂空间结构模拟精确化、消光特性影响因素分析多元性、消光特性测试标准化方面的发展趋势,以期为新型消光材料的制备和改进等提供有益参考。
顾有林张熙胡以华孟凡昊陈国龙丁婉莹王思雨
关键词:烟幕复折射率

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