Stable model categories are categories of modules

A stable model category is a setting for homotopy theory where the suspension functor is invertible. The prototypical examples are the category of spectra in the sense of stable homotopy theory and the category of unbounded chain complexes of modules over a ring. In this paper we develop methods for deciding when two stable model categories represent ‘the same homotopy theory’. We show that stable model categories with a single compact generator are equivalent to modules over a ring spectrum. More generally stable model categories with a set of generators are characterized as modules over a ‘ring spectrum with several objects’, i.e., as spectrum valued diagram categories. We also prove a Morita theorem which shows how equivalences between module categories over ring spectra can be realized by smashing with a pair of bimodules. Finally, we characterize stable model categories which represent the derived category of a ring. This is a slight generalization of Rickard's work on derived equivalent rings. We also include a proof of the model category equivalence of modules over the Eilenberg-Mac Lane spectrum HR and (unbounded) chain complexes of R-modules for a ring R.     

光学双稳性临界点的相变行为

本文详细地讨论了光学双稳性(OB)的临界现象。理论分析主要以忽略量子涨落的Fokker-Plank方程的静态解为基础。结果发现,OB的临界现象可以纳入Landau二级相变理论的框架,并且有关临界指数之间的关系也服从标度律。 关键词：     

Nucleophilic substitution in 5,6,7,8-tetrafluoro- and 6,7-difluoro-1,2,3,4-tetrahydro-9-alkenyl-1,4-methanonaphthalenes and related compounds. A search for homoallylic conjugation

The second-order rate constants for the nucleophilic replacement of fluorine by isopropoxide in 5,6,7,8-tetrafluoro- and 6,7,-difluoro-1,2,3,4-tetrahydro-9-alkenyl-1,4-methanonaphthalenes and related 9-alkyl systems have been measured. A factor of 6 - 7 separates the most reactive compounds [the 9- (4′-trifluoromethylbenzylidene) derivatives] from the least reactive compounds [the syn-9-isopropyl derivatives] in both the tetrafluoro- and difluoro-series. It is concluded for these small reactivity differences.     

A preliminary observation of additive thermodynamic contribution of pendant arms to the complexation of calixarene derivatives with mercury(II)

An additive thermodynamic contribution of pendant arms to the complexation of calixarene derivatives with mercury(II) in acetonitrile is for the first time demonstrated.     

A facile approach to architecturally defined nanoparticles via intramolecular chain collapse

A novel approach is presented for the controlled intramolecular collapse of linear polymer chains to give well-defined single-molecule nanoparticles whose structure is directly related to the original linear polymer. By employing a combination of living free radical polymerization and benzocyclobutene (BCB) chemistry, nanoparticles can be routinely prepared in multigram quantities with the size being accurately controlled by either the initial degree of polymerization of the linear chain or the level of incorporation of the BCB coupling groups. The latter also allows the cross-link density of the final nanoparticles to be manipulated. In analogy with dendritic macromolecules, a significant reduction of up to 75% in the hydrodynamic volume is observed on going from the starting random coil linear chains to the corresponding nanoparticles. The facile nature of the living free radical process also permits wide variation in monomer selection and functional group incorporation and allows novel macromolecular architectures to be prepared. Furthermore, the use of block copolymers functionalized with benzocyclobutene groups in only one of the blocks gives, after intramolecular collapse, a hybrid architecture in which a single linear polymer chain is attached to the globular nanoparticle.     

Optical-optical double-resonance spectroscopy of BaO: The low-lying states

Optical-optical double-resonance (OODR) induced photoluminescence into the lowest excited electronic states of BaO—a³Σ⁺, A¹Σ⁺, b³Π, and $\text{A′}{}^1\text{Π}$—from C¹Σ⁺ is described. These low-lying states are deperturbed to obtain spectroscopic constants and potential energy curves:

     

7.

Positronium production at a carbon-oxygen interface     

Rice-Evans PC  Haynes CE  Al-Qaradawi I  El Khangi FA  Evans HE  Smith DL 《Physical review. B, Condensed matter》1992,46(21):14178-14181

     

8.

Hydrogen and deuterium diffusion in non-stoichiometric spinel     

Geoffrey D. Bromiley  Jennifer Brooke  Simon C. Kohn 《高压研究》2017,37(3):360-376

High pressure/temperature annealing experiments are used to determine diffusivities of H⁺ and D⁺ in non-stoichiometric spinel, a low-pressure analogue for nominally anhydrous minerals in Earth’s mantle. Data are fitted to the following Arrhenius law: Diffusivity (m²/s)?=?4?±?1?×?10^?12 exp(?54?±?2 kJ?mol^?1/RT). At low temperatures, H⁺ and D⁺ diffusion in non-stoichiometric spinel is charge balanced by flux of O vacancies, with infrared data consistent with protonation of both octahedral and tetrahedral O–O edges in non-stoichiometric spinel, and additional fine structure due to Mg–Al mixing and/or coupling of structurally incorporated H⁺ with cation vacancies. Absence of changes in the fine structure of O–H absorption bands indicates that H⁺ can become locally coupled and uncoupled to other defects during bulk diffusion. As such, proton conductivity in spinel group minerals, arising from faster flux of uncoupled H⁺, can only be calculated from H⁺ mobility data if the extent of defect coupling is constrained.     

9.

氮氧自由基研究XVII:水溶液中哌啶氮氧自由基的电化学行为和自衰变动力学研究     

刘有成  张发  江致勤 《化学学报》1987,45(4):477-483

循环伏安法研究表明,2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基和2,2,6,6-四甲基-4-氧哌啶-1-氧自由基,在水溶液中的单电子氧化电极反应的可逆性随介质酸性,扫描速度和自由基浓度增加而增加,表明电极氧化产物可进一步发生化学反应.     

10.

指向学习体验的物质及其转化复习的教学实践——以“钠及其化合物”为例     

法浩  刘翠 《化学教育》2022,43(7):15-20

学习体验是学生对学习内容、过程、方法、意义的自我感受和评估,对学生学习志趣、学习素养提升有积极正向作用。以钠及其化合物复习为例,将各类别物质间转化关系的构建、物质制备原理和条件的优选作为学习体验对象,依据学习体验的内在发展历程设计学习任务及活动,引导学生亲身体验学科认知方式、学科思维方法、学科应用价值,评价体验结果,激励学生自主学习发生。     

1 [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] 下一页 » 末  页»

	$\text{a}{}^3\text{Σ}{}^{\mathrm{+}}$	$\text{A}{}^1\text{Σ}{}^{\mathrm{+}}$	$\text{b}{}^3\text{Π}$	$\text{A′}{}^1\text{Π}$
$\text{T}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	16 596(3)	16 807.345(10)	17 502.6(10)	17 619.7(2)
$\text{ω}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	469.0(7)	499.620(19)	447.62(8)	447.95(22)
$\text{ω}{}_{\mathrm{<mtext>e</mtext>}}\text{x}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	1.48(4)	1.716(8)	2.287(12)	2.139(8)
$\text{ω}{}_{\mathrm{<mtext>e</mtext>}}\text{y}{}_{\mathrm{<mtext>e</mtext>}}\text{× 10}{}^2\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$		2.14(9)		1.02(3)
$\text{B}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	0.2594(5)	0.2583908(26)	0.22426(16)	0.22385(16)
$\text{α}{}_{\mathrm{<mtext>e</mtext>}}\text{× 10}{}^3\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	1.44(5)	1.111(3)	1.18(4)	1.15(4)
$\text{γ}{}_{\mathrm{<mtext>e</mtext>}}\text{× 10}{}^6\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$		7.0(7)		?4.0(21)
$\text{R}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{A}\text{?}\text{)}$	2.1294(20)	2.133512(11)	2.2901(8)	2.2922(8)

Hydrogen and deuterium diffusion in non-stoichiometric spinel

High pressure/temperature annealing experiments are used to determine diffusivities of H⁺ and D⁺ in non-stoichiometric spinel, a low-pressure analogue for nominally anhydrous minerals in Earth’s mantle. Data are fitted to the following Arrhenius law: Diffusivity (m²/s)?=?4?±?1?×?10^?12 exp(?54?±?2 kJ?mol^?1/RT). At low temperatures, H⁺ and D⁺ diffusion in non-stoichiometric spinel is charge balanced by flux of O vacancies, with infrared data consistent with protonation of both octahedral and tetrahedral O–O edges in non-stoichiometric spinel, and additional fine structure due to Mg–Al mixing and/or coupling of structurally incorporated H⁺ with cation vacancies. Absence of changes in the fine structure of O–H absorption bands indicates that H⁺ can become locally coupled and uncoupled to other defects during bulk diffusion. As such, proton conductivity in spinel group minerals, arising from faster flux of uncoupled H⁺, can only be calculated from H⁺ mobility data if the extent of defect coupling is constrained.     

氮氧自由基研究XVII:水溶液中哌啶氮氧自由基的电化学行为和自衰变动力学研究

循环伏安法研究表明,2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基和2,2,6,6-四甲基-4-氧哌啶-1-氧自由基,在水溶液中的单电子氧化电极反应的可逆性随介质酸性,扫描速度和自由基浓度增加而增加,表明电极氧化产物可进一步发生化学反应.     

指向学习体验的物质及其转化复习的教学实践——以“钠及其化合物”为例

学习体验是学生对学习内容、过程、方法、意义的自我感受和评估,对学生学习志趣、学习素养提升有积极正向作用。以钠及其化合物复习为例,将各类别物质间转化关系的构建、物质制备原理和条件的优选作为学习体验对象,依据学习体验的内在发展历程设计学习任务及活动,引导学生亲身体验学科认知方式、学科思维方法、学科应用价值,评价体验结果,激励学生自主学习发生。