Spatial Mixing and Non-local Markov chains

We consider spin systems with nearest-neighbor interactions on an $n$-vertex $d$-dimensional cube of the integer lattice graph $\mathbb{Z}^d$. We study the effects that exponential decay with distance of spin correlations, specifically the strong spatial mixing condition (SSM), has on the rate of convergence to equilibrium distribution of non-local Markov chains. We prove that SSM implies $O(\log n)$ mixing of a block dynamics whose steps can be implemented efficiently. We then develop a methodology, consisting of several new comparison inequalities concerning various block dynamics, that allow us to extend this result to other non-local dynamics. As a first application of our method we prove that, if SSM holds, then the relaxation time (i.e., the inverse spectral gap) of general block dynamics is $O(r)$, where $r$ is the number of blocks. A second application of our technology concerns the Swendsen-Wang dynamics for the ferromagnetic Ising and Potts models. We show that SSM implies an $O(1)$ bound for the relaxation time. As a by-product of this implication we observe that the relaxation time of the Swendsen-Wang dynamics in square boxes of $\mathbb{Z}^2$ is $O(1)$ throughout the subcritical regime of the $q$-state Potts model, for all $q \ge 2$. We also prove that for monotone spin systems SSM implies that the mixing time of systematic scan dynamics is $O(\log n (\log \log n)^2)$. Systematic scan dynamics are widely employed in practice but have proved hard to analyze. Our proofs use a variety of techniques for the analysis of Markov chains including coupling, functional analysis and linear algebra

A simple preconditioner for a discontinuous Galerkin method for the Stokes problem

In this paper we construct Discontinuous Galerkin approximations of the Stokes problem where the velocity field is H(div)-conforming. This implies that the velocity solution is divergence-free in the whole domain. This property can be exploited to design a simple and effective preconditioner for the final linear system.Comment: 27 pages, 4 figure

Effect of Shear Stress on ecNOS Expression and Dilation in Soleus Feed Arteries

Shear stress causes artery dilation and increased expression of endothelial cell nitric oxide synthase (ecNOS) in coronary and placental arteries. We sought to determine the importance of shear stress in maintaining normal dilation and normal levels of ecNOS in rat soleus feed arteries (SFA). SFA were isolated from male Sprague-Dawley rats and cannulated for in vitro microscopy (Fig. 6). SFA were exposed to no shear stress, low shear stress, or high shear stress conditions for 4 hours. After 4 hours, endothelium-dependent dilation (acetylcholine: ACh) and endothelium-independent dilation (sodium nitroprusside: SNP) were tested. Arteries were then uncannulated, mRNA was isolated, and RT-PCR for ecNOS mRNA was performed to determine whether shear stress altered ecNOS gene expression. Shear stress did not alter dilation to ACh, but dilation to SNP was greater in the high shear stress arteries. ecNOS mRNA content was greater in high shear stress arteries than low shear stress arteries. These data indicate that altered wall shear stress conditions alter ecNOS gene expression and vascular smooth muscle cell function

Notes on and lectotypification of Augusto Weberbauer’s collections of Peruvian Ericaceae

Se documenta las 108 colecciones de Ericaceae realizadas por Augusto Weberbauer en el Perú, 48 de las cuales están depositadas en MOL. Del total de estas Ericaceae recolectadas por Weberbauer, se designan aquí como lectotipos 18 colecciones en MOL, 7 en NY, 2 en G, 2 en US y 1 en F.The Ericaceae collections of Augusto Weberbauer from Peru are documented as 108 in number, of which 48 are currently located at MOL. Of these Weberbauer Ericaceae collections, 18 at MOL, 7 at NY, 2 at G, 2 at US, and 1 at F are herein newly designated as lectotypes

New locality record of Psomophis genimaculatus (Squamata, Dipsadidae) in Argentina

Se presenta un nuevo registro de Psomophis genimaculatus (Boettger, 1885). Esta serpiente está categorizada como insuficientemente conocida en Argentina. Se colectó un espécimen en Campo Largo, Provincia de Chaco, Argentina, cubriendo un vacío en el área de distribución de la especie entre los puntos extremos de su rango de distribución en Argentina

Texture changes during chilled storage of wild and farmed blacspot seabream (Pagellus bogaraveo) fed different diets

The impact of changes in dietary lipids and protein sources on texture was evaluated on farmed blackspot seabream (Pagellus bogaraveo) throughout 14 days of ice storage and compared with wild fish. A commercial diet formulated with a high proportion of lipids, and two diets formulated with an important reduction of lipid levels by 60% and adding either plant protein sources (LL diet) or fishmeal (LL + diet) were supplied during growth until commercial size was attained. In the wild fish, the raw fillet hardness was significantly higher than in farmed fish during the entire ice-storage period. In the farmed fish, an increase of muscle lipid accumulation and change of fiber density were responsible for the variations in texture in the raw fillet. The highest reduction was found in fish fed with diets LL+ and LL. The texture parameters studied on the cooked fillets showed no significant differences, neither attributable to the diets nor to the ice-storage period.JUNTA ASESORA DE CULTIVOS MARINOS (JACUMAR)Postprin

Your innovation or mine? The effects of partner diversity on product and process innovation

[EN] Despite a fundamental revolution in digital technology, along with an ancillary reduction in the cost of transmitting knowledge, the innovation literature on knowledge collaboration continues to hold on to the spatial localization of knowledge collaboration as a truism. Drawing on the open innovation literature and knowledge-based view of firm innovation, this study explores key boundary conditions affecting the relationship between research and development (R&D) collaboration breadth, and product and process innovation. Using a large-scale survey consisting of 25,813 observations of 14,784 firms in the United Kingdom during 2004–2020, we demonstrate that the breadth of knowledge collaboration with regional, national, and international partners directly affects product and process innovation. However, this relationship depends on the geographical location of the collaboration partner, the type of partner, and the firm's absorptive capacity. We found diminishing marginal returns to knowledge collaboration breadth for regional partners in product innovation, and an inverted U-shaped relationship in R&D collaboration breadth with regional partners for process innovation and for national and international partners for product and process innovation. While investment in digital technologies only shifts the curve upwards, it is unlikely to change the direction of the relationship between R&D collaboration and a type of innovation outcome. On the contrary, an increase in the share of science, technology, engineering, and math graduates enables firms to leverage the negative effect of R&D collaboration breadth nationally and specifically for process innovation. Investment in digital technology and human capital increases absorptive capacity and reduces the transaction costs associated with oversearch and limited managerial capabilities and resources.S

A Schoolwide Tiered Intervention for Increasing Fruit and Vegetable Consumption

Childhood obesity rates in the U.S. are increasing. Increasing intake of fruits and vegetables is one method to combat obesity. The purpose of this study was to examine a tiered approach to fruit and vegetable consumption with 26 children in an inclusive preschool. The first tier included ongoing availability and opportunity to eat fruits and vegetables (exposure). The second tier included programmed consequences (a reward system). A multiple baseline across children and classrooms was used to evaluate the effect of the interventions. The tier one intervention was effective for nine children and tier two was effective for six children. Eleven children, however, did not respond to either condition. Results are discussed in the context of previous research and tertiary interventions