442 research outputs found
Homotopy Theory of Strong and Weak Topological Insulators
We use homotopy theory to extend the notion of strong and weak topological
insulators to the non-stable regime (low numbers of occupied/empty energy
bands). We show that for strong topological insulators in d spatial dimensions
to be "truly d-dimensional", i.e. not realizable by stacking lower-dimensional
insulators, a more restrictive definition of "strong" is required. However,
this does not exclude weak topological insulators from being "truly
d-dimensional", which we demonstrate by an example. Additionally, we prove some
useful technical results, including the homotopy theoretic derivation of the
factorization of invariants over the torus into invariants over spheres in the
stable regime, as well as the rigorous justification of replacing by
and by as is common in the current
literature.Comment: 11 pages, 3 figure
Hacia un modelo de análisis de políticas públicas operativ : Un enfoque basado en los actores, sus recursos y las instituciones
Towards an operative analysis of public policies: An approach focused on actors, resources and institutions. This article develops an analytical model which is centred on the individual and collective behaviour of actors involved during different stages of public policy. We postulate that the content and institutional characteristics of public action (dependent variable) are the result of interactions between political-administrative authorities, on the one hand, and, on the other, social groups which cause or suffer the negative effects of a collective problem which public action attempts to resolve (independent variables). The 'game' of the actors depends not only on their particular interests, but also on their resources (money, time, consensus,
organization, rights, infrastructure, information, personnel, strength, political support) which they are able to exploit to defend their positions, as well as on the institutional rules which frame these policy games
Equivariant cohomology and analytic descriptions of ring isomorphisms
In this paper we consider a class of connected closed -manifolds with a
non-empty finite fixed point set, each of which is totally non-homologous
to zero in (or -equivariantly formal), where . With the
help of the equivariant index, we give an explicit description of the
equivariant cohomology of such a -manifold in terms of algebra, so that we
can obtain analytic descriptions of ring isomorphisms among equivariant
cohomology rings of such -manifolds, and a necessary and sufficient
condition that the equivariant cohomology rings of such two -manifolds are
isomorphic. This also leads us to analyze how many there are equivariant
cohomology rings up to isomorphism for such -manifolds in 2- and
3-dimensional cases.Comment: 20 pages, updated version with two references adde
Quantum symmetric pairs and representations of double affine Hecke algebras of type
We build representations of the affine and double affine braid groups and
Hecke algebras of type , based upon the theory of quantum symmetric
pairs . In the case , our constructions provide a
quantization of the representations constructed by Etingof, Freund and Ma in
arXiv:0801.1530, and also a type generalization of the results in
arXiv:0805.2766.Comment: Final version, to appear in Selecta Mathematic
The switch-like expression of heme-regulated kinase 1 mediates neuronal proteostasis following proteasome inhibition
We examined the feedback between the major protein degradation pathway, the ubiquitin-proteasome system (UPS), and protein synthesis in rat and mouse neurons. When protein degradation was inhibited, we observed a coordinate dramatic reduction in nascent protein synthesis in neuronal cell bodies and dendrites. The mechanism for translation inhibition involved the phosphorylation of eIF2alpha, surprisingly mediated by eIF2alpha kinase 1, or heme-regulated kinase inhibitor (HRI). Under basal conditions, neuronal expression of HRI is barely detectable. Following proteasome inhibition, HRI protein levels increase owing to stabilization of HRI and enhanced translation, likely via the increased availability of tRNAs for its rare codons. Once expressed, HRI is constitutively active in neurons because endogenous heme levels are so low; HRI activity results in eIF2alpha phosphorylation and the resulting inhibition of translation. These data demonstrate a novel role for neuronal HRI that senses and responds to compromised function of the proteasome to restore proteostasis
Exploring Tourist Experiences of Virtual Reality in a Rural Destination: A Place Attachment Theory Perspective
In tourism, virtual reality (VR) experience gained a lot of interest recently. It is argued that positive tourist experience might enhance place attachment (PA) which can be described as the emotional bond between people and places. However, PA studies neglects virtual environments and thus studies in a VR context are scarce. Therefore the present study, explores to what extend VR increases tourist experience and affects tourist’s PA at rural destination of Lake District National Park (LDNP). For this purpose semi-structured interviews were conducted in July 2017. Data were analyzed using thematic analyses and first finding shows that VR enhances tourist experience and shows a positive influence on PA. Two main themes were identified; enhanced spatial cognition and positive feelings. The theoretical contribution is to expand PA theory considering virtual environments. Managerial implications include using VR as a marketing tool for increasing tourist experience at the destination
Employee Innovation in the Hospitality Industry: the Mediating Role of Psychological Safety
In the current turbulent and highly competitive environment, innovation can be considered a strategic weapon that enables hotels to survive, compete, and succeed. Innovation has been advocated to enhance hotels’ products, services, productions, processes, and overall performance. Innovation activities can take place as a result of employees’ behaviour, hence there is a call for greater attention to employees, in order to enhance hotel performance. Since innovation activities may involve uncertainty and risk, it is crucial to understand what makes employees feel safe, also referred to in literature as psychological safety, and encouraged to engage in the innovative behaviour. This conceptual paper presents an exploration of the factors that could encourage employee innovation in the hospitality industry. This relationship is supposedly mediated by psychological safety of the employees. The model propose seven essential elements that can promote innovative behaviour in the hospitality industry. Support and motivation from the management, high-quality relationships amongst members at work, autonomy, role expectation, and proactive personality, as an interpersonal trait, are all proposed to be positively associated with psychological safety and employee innovation, whereas openness to experiences and challenges at work are suggested to be positively associated only with employee innovation. Thus, understanding what promotes innovative behaviour will help hoteliers to cultivate and encourage the innovative behaviour amongst hotels’ employees, which can, in turn, enhance hotels’ services quality and performance
The translatome of neuronal cell bodies, dendrites,and axons
To form synaptic connections and store information, neurons continuously remodel their proteomes. The impressive length of dendrites and axons imposes logistical challenges to maintain synaptic proteins at locations remote from the transcription source (the nucleus). The discovery of thousands of messenger RNAs (mRNAs) near synapses suggested that neurons overcome distance and gain autonomy by producing proteins locally. It is not generally known, however, if, how, and when localized mRNAs are translated into protein. To investigate the translational landscape in neuronal subregions, we performed simultaneous RNA sequencing (RNA-seq) and ribosome sequencing (Ribo-seq) from microdissected rodent brain slices to identify and quantify the transcriptome and translatome in cell bodies (somata) as well as dendrites and axons (neuropil). Thousands of transcripts were differentially translated between somatic and synaptic regions, with many scaffold and signaling molecules displaying increased translation levels in the neuropil. Most translational changes between compartments could be accounted for by differences in RNA abundance. Pervasive translational regulation was observed in both somata and neuropil influenced by specific mRNA features (e.g., untranslated region [UTR] length, RNA-binding protein [RBP] motifs, and upstream open reading frames [uORFs]). For over 800 mRNAs, the dominant source of translation was the neuropil. We constructed a searchable and interactive database for exploring mRNA transcripts and their translation levels in the somata and neuropil [MPI Brain Research, The mRNA translation landscape in the synaptic neuropil. https://public.brain.mpg.de/dashapps/localseq/ Accessed 5 October 2021]. Overall, our findings emphasize the substantial contribution of local translation to maintaining synaptic protein levels and indicate that on-site translational control is an important mechanism to control synaptic strength
A new method to quantify and compare the multiple components of fitness-A study case with kelp niche partition by divergent microstage adaptations to Temperature
Point 1 Management of crops, commercialized or protected species, plagues or life-cycle evolution are subjects requiring comparisons among different demographic strategies. The simpler methods fail in relating changes in vital rates with changes in population viability whereas more complex methods lack accuracy by neglecting interactions among vital rates. Point 2 The difference between the fitness (evaluated by the population growth rate.) of two alternative demographies is decomposed into the contributions of the differences between the pair-wised vital rates and their interactions. This is achieved through a full Taylor expansion (i.e. remainder = 0) of the demographic model. The significance of each term is determined by permutation tests under the null hypothesis that all demographies come from the same pool. Point 3 An example is given with periodic demographic matrices of the microscopic haploid phase of two kelp cryptic species observed to partition their niche occupation along the Chilean coast. The method provided clear and synthetic results showing conditional differentiation of reproduction is an important driver for their differences in fitness along the latitudinal temperature gradient. But it also demonstrated that interactions among vital rates cannot be neglected as they compose a significant part of the differences between demographies. Point 4 This method allows researchers to access the effects of multiple effective changes in a life-cycle from only two experiments. Evolutionists can determine with confidence the effective causes for changes in fitness whereas population managers can determine best strategies from simpler experimental designs.CONICYT-FRENCH EMBASSADY Ph.D. gran
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