检索结果-南通市图书馆

Neural Regeneration Research 2025年第9期20卷 2591-2593页

作者： Alena Salasova anders Nykjær Danish Research Institute of Translational Neuroscience DANDRITE-Nordic EMBL Partnership for Molecular Medicine and Centre of Excellence PROMEMODepartment of BiomedicineAarhus UniversityAarhusDenmark

The formation of the mammalian nervous system and its maturation into sensory,motor,cognitive,and behavioral circuits is a complex process that begins during early embryogenesis and lasts until young *** neurodevelopm... 详细信息

关键词： progr jointly CS2

Typicality at quantum-critical points

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2018年第8期27卷 517-528页

作者： Lu Liu anders w Sandvik wenan Guo Department of Physics Beijing Normal UniversityBeijing 100875China Department of Physics Boston University590 Commonwealth AvenueBostonMassachusetts 02215USA Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190China

we discuss the concept of typicality of quantum states at quantum-critical points, using projector Monte Carlo simu- lations of an S ---- 1/2 bilayer Heisenberg antiferromagnet as an illustration. with the projection （imaginary） time t scaled as t= aLz, L being the system length and z the dynamic critical exponent （which takes the value z = 1 in the bilayer model studied here）, a critical point can be identified which asymptotically flows to the correct location and universality class with increasing L, independently of the prefactor a and the initial state. Varying the proportionality factor a and the initial state only changes the cross-over behavior into the asymptotic large-L behavior. In some cases, choosing an optimal factor a may also lead to the vanishing of the leading finite-size corrections. The observation of typicality can be used to speed up simulations of quantum criticality, not only within the Monte Carlo approach but also with other numerical methods where imaginary-time evolution is employed, e.g., tensor network states, as it is not necessary to evolve fully to the ground state but only for sufficiently long times to reach the typicality regime.

关键词： typicality quantum criticality bilayer Heisenberg antiferromagnet model imaginary projectingtime, projecting quantum Monte Carlo simulation

Consistent Scaling Exponents at the Deconfined Quantum-Critical Point

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2020年第5期37卷 93-97页

作者： anders w.Sandvik Bowen Zhao Department of Physics Boston UniversityBostonMassachusetts 02215USA Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190

we report a quantum Monte Carlo study of the phase transition between antiferromagnetic and valence-bond solid ground states in the square-lattice S=1/2 J-Q *** critical correlation function of the Q terms gives a scaling dimension corresponding to the value v=0.455±0.002 of the correlation-length *** value agrees with previous(less precise)results from conventional methods,e.g.,finite-size scaling of the nearcritical order *** also study the Q-derivatives of the Binder cumulants of the order parameters for L2 lattices with L up to *** slope grows as L1/v with a value of v consistent with the scaling dimension of the Q *** are no indications of runaway flow to a first-order phase *** mutually consistent estimates of v provide compelling support for a continuous deconfined quantum-critical point.

关键词： transition. confined scaling

Quantum Spin Liquid Phase in the Shastry–Sutherland Model Detected by an Improved Level Spectroscopic Method

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2022年第7期39卷 105-116页

作者： Ling wang Yalei Zhang anders w.Sandvik Department of Physics Zhejiang UniversityHangzhou 310000China Beijing Computational Science Research Center Beijing 100193China Department of Physics Boston UniversityBostonMassachusetts 02215USA Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190China

we study the spin-1/2 two-dimensional Shastry–Sutherland spin model by exact diagonalization of clusters with periodic boundary conditions, developing an improved level spectroscopic technique using energy gaps between states with different quantum numbers. The crossing points of some of the relative(composite) gaps have much weaker finite-size drifts than the normally used gaps defined only with respect to the ground state, thus allowing precise determination of quantum critical points even with small clusters. Our results support the picture of a spin liquid phase intervening between the well-known plaquette-singlet and antiferromagnetic ground states, with phase boundaries in almost perfect agreement with a recent density matrix renormalization group study, where much larger cylindrical lattices were used [J. Yang et al., Phys. Rev. B 105, L060409(2022)]. The method of using composite low-energy gaps to reduce scaling corrections has potentially broad applications in numerical studies of quantum critical phenomena.

关键词： red SSM Sutherland Model Detected by an Improved Level Spectroscopic Method Quantum Spin Liquid Phase in the Shastry Model

Tunable deconfined quantum criticality and interplay of different valence-bond solid phases

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2020年第5期29卷 52-65页

作者： Bowen Zhao Jun Takahashi anders w.Sandvik Department of Physics Boston University590 Commonwealth AvenueBostonMassachusetts 02215USA Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190China

we use quantum Monte Carlo simulations to study an S = 1/2 spin model with competing multi-spin interactions. we find a quantum phase transition between a columnar valence-bond solid(cVBS) and a Néel antiferromagnet(AFM), as in the scenario of deconfined quantum-critical points, as well as a transition between the AFM and a staggered valence-bond solid(sVBS). By continuously varying a parameter, the sVBS–AFM and AFM–cVBS boundaries merge into a direct sVBS–cVBS transition. Unlike previous models with putative deconfined AFM–cVBS transitions, e.g., the standard J–Q model,in our extended J–Q model with competing cVBS and sVBS inducing terms the transition can be tuned from continuous to first-order. we find the expected emergent U(1) symmetry of the microscopically Z4 symmetric cVBS order parameter when the transition is continuous. In contrast, when the transition changes to first-order, the clock-like Z4 fluctuations are absent and there is no emergent higher symmetry. we argue that the confined spinons in the sVBS phase are *** also present results for an SU(3) symmetric model with a similar phase diagram. The new family of models can serve as a useful tool for further investigating open questions related to deconfined quantum criticality and its associated emergent symmetries.

关键词： quantum phase transitions deconfined quantum criticality quantum spin systems quantum Monte Carlo simulations

why are sexually selected weapons almost absent in females？

在线全文

学校读者我要写书评

暂无评论

Current Zoology 2013年第4期59卷 564-568页

作者： anders BERGLUND Department of Ecology and Genetics/Animal Ecology Uppsala University Norbyv. 18d 752 36 Uppsala Sweden

In sex role reversed species, predominantly females evolve sexually selected traits, such as ornaments and/or weapons. Female ornaments are common and their function well documented in many species, whether sex role reversed or not. However, sexually selected female weapons seem totally absent except for small wing spurs in three jacana species, present in both males and females. This poor female weaponry is in sharp contrast to the situation in species with conventional sex roles： males com- monly have evolved sexually selected weapons as well as ornaments. At the same time, females in many taxa have naturally se- lected weapons, used in competition over resources or in predator defence. why are sexually selected weapons then so rare, al- most absent, in females？ Here I briefly review weaponry in females and the function of these weapons, conclude that the near ab- sence of sexually selected weapons begs an explanation, and suggest that costs of sexually selected weapons may exceed costs of ornaments. Females are more constrained when evolving sexually selected traits compared to males, at least compared to those males that do not provide direct benefits, as trait costs reduce a female＇s fecundity. I suggest that this constraining trade-off between trait and fecundity restricts females to evolve ornaments but rarely weapons. The same may apply to paternally investing males. whether sexually selected weapons actually are more costly than sexually selected ornaments remains to be investigated

关键词： Sexual selection Female weapons Female ornaments Sex role reversal

Bottom-up approaches to microLEDs emitting red, green and blue light based on GaN nanowires and relaxed InGaN platelets

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2023年第1期32卷 1-10页

作者：毕朝霞 anders Gustafsson Lars Samuelson anders Gustafsson and Lars Samuelson Division of Solid State Physics and NanoLundLund UniversityBox 118SE-22100 LundSweden

Miniaturization of light-emitting diodes(LEDs) with sizes down to a few micrometers has become a hot topic in both academia and industry due to their attractive applications on self-emissive displays for high-definition televisions,augmented/mixed realities and head-up displays, and also on optogenetics, high-speed light communication, etc. The conventional top-down technology uses dry etching to define the LED size, leading to damage to the LED side *** sizes of microLEDs approach the carrier diffusion length, the damaged side walls play an important role, reducing microLED performance significantly from that of large area LEDs. In this paper, we review our efforts on realization of microLEDs by direct bottom-up growth, based on selective area metal–organic vapor phase epitaxy. The individual LEDs based on either GaN nanowires or InGaN platelets are smaller than 1 μm in our approach. Such nano-LEDs can be used as building blocks in arrays to assemble microLEDs with different sizes, avoiding the side wall damage by dry etching encountered for the top-down approach. The technology of InGaN platelets is especially interesting since InGaN quantum wells emitting red, green and blue light can be grown on such platelets with a low-level of strain by changing the indium content in the InGaN platelets. This technology is therefore very attractive for highly efficient microLEDs of three primary colors for displays.

关键词： microLEDs RGB GaN InGaN

Biological consequences of global change for birds

在线全文

学校读者我要写书评

暂无评论

Integrative Zoology 2013年第2期8卷 136-144页

作者： anders Pape MØLLER Department of Ecology Systematics and EvolutionUniversity Paris-SouthOrsay CedexFrance

Climate is currently changing at an unprecedented rate;so also human exploitation is rapidly changing the Earth for agriculture,forestry,fisheries and *** addition,pollution has affected even the most remote ecosystems,as has the omnipresence of humans,with consequences in particular for animals that keep a safe distance from potential predators,including human ***,all of these changes are occurring simultaneously,with increasing intensity,and further deterioration in both the short and the long-term is *** the consequences of these components of global change are relatively well studied on their own,the effects of their interactions,such as the combined effects of climate change and agriculture,or the combined effects of agriculture through nutrient leakage to freshwater and marine ecosystems and fisheries,and the effects of climate change and urbanization,are poorly ***,I provide a brief overview of the effects of climate change on phenology,diversity,abundance,interspecific interactions and population dynamics of birds.I address whether these effects of changing temperatures are direct,or indirect through effects of climate change on the phenology,distribution or abundance of food,parasites and ***,I review interactions between different components of global change.

关键词： climate change direct effects global change indirect effects interactions

Climate-Induced Variability of Sea Level in Stockholm: Influence of Air Temperature and Atmospheric Circulation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2005年第5期22卷 655-664页

作者： Deliang CHEN anders OMSTEDT Earth Sciences Centre Goteborg University Sweden Laboratory for Climate Studies/National Climate Center China Meteorological Administration Beijing 100081

This study is focused on climate-induced variation of sea level in Stockholm during 1873-1995. After the effect of the land uplift, is removed, the residual is characterized and related to large-scale temperature and atmospheric circulation. The residual shows an overall upward trend, although this result depends on the uplift rate used. However, the seasonal distribution of the trend is uneven. There are even two months （June and August） that show a negative trend. The significant trend in August may be linked to fresh water input that is controlled by precipitation. The influence of the atmospheric conditions on the sea level is mainly manifested through zonal winds, vorticity and temperature. while the wind is important in the period January-May, the vorticity plays a main role during June and December. A successful linear multiple-regression model linking the climatic variables （zonal winds, vorticity and mean air temperature during the previous two months） and the sea level is established for each month. An independent verification of the model shows that it has considerable skill in simulating the variability.

关键词： sea level Baltic sea atmospheric circulation temperature Stockholm