IA Scholar Query: Bounds on the bisection width for random d -regular graphs.
https://scholar.archive.org/
Internet Archive Scholar query results feedeninfo@archive.orgTue, 20 Sep 2022 00:00:00 GMTfatcat-scholarhttps://scholar.archive.org/help1440Minimizing Convex Functions with Rational Minimizers
https://scholar.archive.org/work/5kftfwze7jf6bilgtmwu3up65u
Given a separation oracle 𝖲𝖮 for a convex function f defined on ℝ^n that has an integral minimizer inside a box with radius R, we show how to find an exact minimizer of f using at most (a) O(n (n loglog (n)/log (n) + log(R))) calls to 𝖲𝖮 and 𝗉𝗈𝗅𝗒(n, log(R)) arithmetic operations, or (b) O(n log(nR)) calls to 𝖲𝖮 and exp(O(n)) ·𝗉𝗈𝗅𝗒(log(R)) arithmetic operations. When the set of minimizers of f has integral extreme points, our algorithm outputs an integral minimizer of f. This improves upon the previously best oracle complexity of O(n^2 (n + log(R))) for polynomial time algorithms and O(n^2log(nR)) for exponential time algorithms obtained by [Grötschel, Lovász and Schrijver, Prog. Comb. Opt. 1984, Springer 1988] over thirty years ago. Our improvement on Grötschel, Lovász and Schrijver's result generalizes to the setting where the set of minimizers of f is a rational polyhedron with bounded vertex complexity. For the Submodular Function Minimization problem, our result immediately implies a strongly polynomial algorithm that makes at most O(n^3 loglog (n)/log (n)) calls to an evaluation oracle, and an exponential time algorithm that makes at most O(n^2 log(n)) calls to an evaluation oracle. These improve upon the previously best O(n^3 log^2(n)) oracle complexity for strongly polynomial algorithms given in [Lee, Sidford and Wong, FOCS 2015] and [Dadush, Végh and Zambelli, SODA 2018], and an exponential time algorithm with oracle complexity O(n^3 log(n)) given in the former work. Our result is achieved via a reduction to the Shortest Vector Problem in lattices. We analyze its oracle complexity using a potential function that simultaneously captures the size of the search set and the density of the lattice.Haotian Jiangwork_5kftfwze7jf6bilgtmwu3up65uTue, 20 Sep 2022 00:00:00 GMTSharp threshold for the FA-2f kinetically constrained model
https://scholar.archive.org/work/kdtgztej7fdebpjkqm3pq4as3a
The Fredrickson-Andersen 2-spin facilitated model on ℤ^d (FA-2f) is a paradigmatic interacting particle system with kinetic constraints (KCM) featuring dynamical facilitation, an important mechanism in condensed matter physics. In FA-2f a site may change its state only if at least two of its nearest neighbours are empty. Although the process is reversible w.r.t. a product Bernoulli measure, it is not attractive and features degenerate jump rates and anomalous divergence of characteristic time scales as the density q of empty sites tends to 0. A natural random variable encoding the above features is τ_0, the first time at which the origin becomes empty for the stationary process. Our main result is the sharp threshold τ_0=exp(d·λ(d,2)+o(1)/q^1/(d-1)) w.h.p. with λ(d,2) the sharp threshold constant for 2-neighbour bootstrap percolation on ℤ^d, the monotone deterministic automaton counterpart of FA-2f. This is the first sharp result for a critical KCM and it compares with Holroyd's 2003 result on bootstrap percolation and its subsequent improvements. It also settles various controversies accumulated in the physics literature over the last four decades. Furthermore, our novel techniques enable completing the recent ambitious program on the universality phenomenon for critical KCM and establishing sharp thresholds for other two-dimensional KCM.Ivailo Hartarsky, Fabio Martinelli, Cristina Toninelliwork_kdtgztej7fdebpjkqm3pq4as3aTue, 20 Sep 2022 00:00:00 GMTThe ICON-A model for direct QBO simulations on GPUs (version icon-cscs:baf28a514)
https://scholar.archive.org/work/smkqemns4jh35bzblqqem2b5hu
Abstract. Classical numerical models for the global atmosphere, as used for numerical weather forecasting or climate research, have been developed for conventional central processing unit (CPU) architectures. This hinders the employment of such models on current top-performing supercomputers, which achieve their computing power with hybrid architectures, mostly using graphics processing units (GPUs). Thus also scientific applications of such models are restricted to the lesser computer power of CPUs. Here we present the development of a GPU-enabled version of the ICON atmosphere model (ICON-A), motivated by a research project on the quasi-biennial oscillation (QBO), a global-scale wind oscillation in the equatorial stratosphere that depends on a broad spectrum of atmospheric waves, which originates from tropical deep convection. Resolving the relevant scales, from a few kilometers to the size of the globe, is a formidable computational problem, which can only be realized now on top-performing supercomputers. This motivated porting ICON-A, in the specific configuration needed for the research project, in a first step to the GPU architecture of the Piz Daint computer at the Swiss National Supercomputing Centre and in a second step to the JUWELS Booster computer at the Forschungszentrum Jülich. On Piz Daint, the ported code achieves a single-node GPU vs. CPU speedup factor of 6.4 and allows for global experiments at a horizontal resolution of 5 km on 1024 computing nodes with 1 GPU per node with a turnover of 48 simulated days per day. On JUWELS Booster, the more modern hardware in combination with an upgraded code base allows for simulations at the same resolution on 128 computing nodes with 4 GPUs per node and a turnover of 133 simulated days per day. Additionally, the code still remains functional on CPUs, as is demonstrated by additional experiments on the Levante compute system at the German Climate Computing Center. While the application shows good weak scaling over the tested 16-fold increase in grid size and node count, making also higher resolved global simulations possible, the strong scaling on GPUs is relatively poor, which limits the options to increase turnover with more nodes. Initial experiments demonstrate that the ICON-A model can simulate downward-propagating QBO jets, which are driven by wave–mean flow interaction.Marco A. Giorgetta, William Sawyer, Xavier Lapillonne, Panagiotis Adamidis, Dmitry Alexeev, Valentin Clément, Remo Dietlicher, Jan Frederik Engels, Monika Esch, Henning Franke, Claudia Frauen, Walter M. Hannah, Benjamin R. Hillman, Luis Kornblueh, Philippe Marti, Matthew R. Norman, Robert Pincus, Sebastian Rast, Daniel Reinert, Reiner Schnur, Uwe Schulzweida, Bjorn Stevenswork_smkqemns4jh35bzblqqem2b5huFri, 16 Sep 2022 00:00:00 GMTExpectation–Maximization-Based Simultaneous Localization and Mapping for Millimeter-Wave Communication Systems
https://scholar.archive.org/work/vaqnauofajhcdgp7wdyfku5y4q
In this paper, we proposed a novel expectation–maximization-based simultaneous localization and mapping (SLAM) algorithm for millimeter-wave (mmW) communication systems. By fully exploiting the geometric relationship among the access point (AP) positions, the angle difference of arrival (ADOA) from the APs and the mobile terminal (MT) position, and regarding the MT positions as the latent variable of the AP positions, the proposed algorithm first reformulates the SLAM problem as the maximum likelihood joint estimation over both the AP positions and the MT positions in a latent variable model. Then, it employs a feasible stochastic approximation expectation–maximization (EM) method to estimate the AP positions. Specifically, the stochastic Monte Carlo approximation is employed to obtain the intractable expectation of the MT positions' posterior probability in the E-step, and the gradient descent-based optimization is used as a viable substitute for estimating the high-dimensional AP positions in the M-step. Further, it estimates the MT positions and constructs the indoor map based on the estimated AP topology. Due to the efficient processing capability of the stochastic approximation EM method and taking full advantage of the abundant spatial information in the crowd-sourcing ADOA data, the proposed method can achieve a better positioning and mapping performance than the existing geometry-based mmW SLAM method, which usually has to compromise between the computation complexity and the estimation performance. The simulation results confirm the effectiveness of the proposed algorithm.Lu Chen, Zhigang Chen, Zhi Jiwork_vaqnauofajhcdgp7wdyfku5y4qWed, 14 Sep 2022 00:00:00 GMTMachine Learning of Implicit Combinatorial Rules in Mechanical Metamaterials
https://scholar.archive.org/work/s3szepsfhfd5tpvvwxhnmpe3sy
Combinatorial problems arising in puzzles, origami, and (meta)material design have rare sets of solutions, which define complex and sharply delineated boundaries in configuration space. These boundaries are difficult to capture with conventional statistical and numerical methods. Here we show that convolutional neural networks can learn to recognize these boundaries for combinatorial mechanical metamaterials, down to finest detail, despite using heavily undersampled training sets, and can successfully generalize. This suggests that the network infers the underlying combinatorial rules from the sparse training set, opening up new possibilities for complex design of (meta)materials.Ryan van Mastrigt, Marjolein Dijkstra, Martin van Hecke, Corentin Coulaiswork_s3szepsfhfd5tpvvwxhnmpe3syTue, 13 Sep 2022 00:00:00 GMTThe Caves Branch Archaeological Survey Project: A Report of the 2009 Field Season
https://scholar.archive.org/work/vkd7fctezfe7ffff2hvtaw6vlu
The first season of the Caves Branch Archaeological Survey (CBAS) project was an intense and productive one. As an outgrowth of work initiated in the area by the Belize Valley Archaeological Reconnaissance (BVAR) project in the 1990s, the CBAS project's goal is to produce a broad reconstruction of pre-Hispanic cultural patterns in and around the Caves Branch River Valley. With this overarching objective in mind, we began to develop an occupational chronology for the area's surface sites, continued building a timeline of use of the region's cave sites, and explored relationships between sites of different types and sizes. Initiation of these activities in 2009 represents part of a longer-term effort to amass comparative data sets that will illuminate connections between ancient communities in the Caves Branch, Roaring Creek, and Sibun River drainages. It is our hope that these efforts will ultimately allow for broad, supra-site level reconstructions of pre-Hispanic Maya community patterns in this part of the southern lowlands. In an effort to achieve such a regional perspective, the project pursued a variety of interrelated activities between May and July of 2009.HC User, Christopher Andres, Gabriel Wrobelwork_vkd7fctezfe7ffff2hvtaw6vluFri, 09 Sep 2022 00:00:00 GMTmmWave Beam Alignment using Hierarchical Codebooks and Successive Subtree Elimination
https://scholar.archive.org/work/tjx6odjzhrgqhoucruwajfczye
We propose a best arm identification multi-armed bandit algorithm in the fixed-confidence setting for mmWave beam alignment initial access called SSE. The algorithm performance approaches that of state-of-the-art Bayesian algorithms at a fraction of the complexity and without requiring channel state information. The algorithm simultaneously exploits the benefits of hierarchical codebooks and the approximate unimodality of rewards to achieve fast beam steering, in a sense that we precisely define to provide fair comparison with existing algorithms. We derive a closed-form sample complexity, which enables tuning of design parameters. We also perform extensive simulations over slow fading channels to demonstrate the appealing performance versus complexity trade-off struck by the algorithm across a wide range of channel conditionsNathan Blinn, Matthieu Blochwork_tjx6odjzhrgqhoucruwajfczyeWed, 07 Sep 2022 00:00:00 GMTEmbodiment Design Cartography: A Conceptual Framework for Design Space Mapping to Support the Development of Physically-Interactive Products
https://scholar.archive.org/work/azuwcact6jbyjeqsxysjm3ku6i
Embodiment design is the process of taking an idea for a product and bringing it into the real world by specifying key parameters. In this process, numerous decisions are made that ultimately lead to a solution. By entering the real world, however, a host of complexities are introduced to the design problem by external actors. The different people that physically interact with the product, as well as the situations for these interactions, may all factor into shaping the way this solution is received in a manner that is outside of the designer's control. To truly understand the outcomes of the options that exist within this solution space, there is a web of considerations that must be navigated in the problem space. Together, the considerations in this problem space and the relations between them, as well as the options in the solution space comprise the overall design space. The term 'cartography' refers to the creation of maps—this dissertation presents a conceptual framework for systematically mapping out this design space such that the paths along this web of considerations may be navigated, and the resulting outcomes that may be achieved are understood. There are existing methods from different design disciplines that can help understand the solution space, however each imparts a distinct, fixed perspective on how it conceives the problem space and therefore only recognizes the portion it considers to be important. The Embodiment Design Cartography framework developed in this dissertation is illustrated by mapping out these methods on a uniform scale that enables their direct comparison and combination. New design methods are also constructed within this framework, which may be tailored to the problem at hand, and more holistically cover the design space without the limiting preconceptions of existing methods. This practice is employed in two case studies for products that exemplify questions in embodiment design. The first regards how tradeoffs between competing outcomes may be successfully negotiated. The s [...]Jesse Velleu, University, Mywork_azuwcact6jbyjeqsxysjm3ku6iTue, 06 Sep 2022 00:00:00 GMTPercolation through Voids around Toroidal Inclusions
https://scholar.archive.org/work/nb2znxaluzcjnclxtmpp6vldge
In the case of media comprised of impermeable particles, fluid flows through voids around impenetrable grains. For sufficiently low concentrations of the latter, spaces around grains join to allow transport on macroscopic scales, whereas greater impenetrable inclusion densities disrupt void networks and block macroscopic fluid flow. A critical grain concentration ρ_c marks the percolation transition or phase boundary separating these two regimes. With a dynamical infiltration technique in which virtual tracer particles explore void spaces, we calculate critical grain concentrations for randomly placed interpenetrating impermeable toroidal inclusions; the latter consist of surfaces of revolution with circular and square cross sections. In this manner, we study for the first time continuum percolation transitions involving non-convex grains. As the radius of revolution increases relative to the length scale of the torus cross section, the tori develop a central hole, a topological transition accompanied by a cusp in the critical porosity for percolation. With a further increase in the radius of revolution, as constituent grains become more ring-like in appearance, we find that the critical porosity converges to that of high aspect ratio cylindrical counterparts only for randomly oriented grains.A. Ballow, P. Linton, D. J. Priour Jrwork_nb2znxaluzcjnclxtmpp6vldgeMon, 22 Aug 2022 00:00:00 GMTswNEMO_v4.0: an ocean model based on NEMO4 for the new-generation Sunway supercomputer
https://scholar.archive.org/work/2zhsvjk7pjg2lfd2e7xer7zime
Abstract. The current large-scale parallel barrier of ocean general circulation models (OGCMs) makes it difficult to meet the computing demand of high resolution. Fully considering both the computational characteristics of OGCMs and the heterogeneous many-core architecture of the new Sunway supercomputer, swNEMO_v4.0, based on NEMO4 (Nucleus for European Modelling of the Ocean version 4), is developed with ultrahigh scalability. Three innovations and breakthroughs are shown in our work: (1) a highly adaptive, efficient four-level parallelization framework for OGCMs is proposed to release a new level of parallelism along the compute-dependency column dimension. (2) A many-core optimization method using blocking by remote memory access (RMA) and a dynamic cache scheduling strategy is applied, effectively utilizing the temporal and spatial locality of data. The test shows that the actual direct memory access (DMA) bandwidth is greater than 90 % of the ideal band-width after optimization, and the maximum is up to 95 %. (3) A mixed-precision optimization method with half, single and double precision is explored, which can effectively improve the computation performance while maintaining the simulated accuracy of OGCMs. The results demonstrate that swNEMO_v4.0 has ultrahigh scalability, achieving up to 99.29 % parallel efficiency with a resolution of 500 m using 27 988 480 cores, reaching the peak performance with 1.97 PFLOPS.Yuejin Ye, Zhenya Song, Shengchang Zhou, Yao Liu, Qi Shu, Bingzhuo Wang, Weiguo Liu, Fangli Qiao, Lanning Wangwork_2zhsvjk7pjg2lfd2e7xer7zimeMon, 25 Jul 2022 00:00:00 GMTSector length distributions of graph states
https://scholar.archive.org/work/piak23a7erfbxfpskrgku6ca6e
The sector length distribution (SLD) of a quantum state is a collection of local unitary invariants that quantify k-body correlations. We show that the SLD of graph states can be derived by solving a graph-theoretical problem. In this way, the mean and variance of the SLD are obtained as simple functions of efficiently computable graph properties. Furthermore, this formulation enables us to derive closed expressions of SLDs for some graph state families. For cluster states, we observe that the SLD is very similar to a binomial distribution, and we argue that this property is typical for graph states in general. Finally, we derive an SLD-based entanglement criterion from the majorization criterion and apply it to derive meaningful noise thresholds for entanglement.Daniel Miller, Daniel Loss, Ivano Tavernelli, Hermann Kampermann, Dagmar Bruß, Nikolai Wyderkawork_piak23a7erfbxfpskrgku6ca6eFri, 15 Jul 2022 00:00:00 GMTDefect Induced Cavitation in Micro-Channels
https://scholar.archive.org/work/pu746zqfnveh7jgmjxgoaqkazu
The thesis examines cavitation from surface protrusions at micro-scales.ANESU JUNIOR KUSANGAYAwork_pu746zqfnveh7jgmjxgoaqkazuWed, 13 Jul 2022 00:00:00 GMTFoundations of Clustering: New Models and Algorithms
https://scholar.archive.org/work/ejn3zmumfzbwvaeircgyztx7ea
In this dissertation, we study clustering, one of the most common unsupervised learning problems. This dissertation covers recent developments in both clustering theory and machine learning practice. In particular, it explores how to bridge the gap between theory and practice by making them benefit from each other. Many clustering algorithms are developed in an application-oriented way lacking the guidance of theory. For some clustering problems it is hard to mathematically characterize what is being optimized. The arising needs in the ML/AI community, such as fairness and scalability, also require updates in current problem formulations. The first few chapters of this dissertation lay the theoretical foundation for multiple clustering problems. We first establish the formal optimization framework. Such a framework gives us conceptual understanding of the problems and becomes the basis for optimization and algorithm design. We then discuss the performance of existing approaches and come up with new algorithms beating the state-of-the-art. Empirical evaluations also verify that the new algorithms perform better in both quality and efficiency, showing it is beneficial to view these problems through the lens of theory. We study one classic clustering problem: hierarchical clustering. Unlike other more well-formulated clustering problems such as k-means, the theoretical study of hierarchical clustering has kicked off recently. The first chapter focuses on new objective function design for hierarchical clustering on point inputs in a Euclidean space. It provides theoretical guarantees for a popular heuristic. The second chapter studies how to incorporate fairness into the hierarchical clustering optimization framework. It defines fair hierarchical clustering trees and discusses how to design algorithms that find fair solutions for previous hierarchical clustering objectives established by the community. Surprisingly, in this setting fairness could be imposed at minimal loss in clustering solution performance. The focu [...]Yuyan Wangwork_ejn3zmumfzbwvaeircgyztx7eaMon, 11 Jul 2022 00:00:00 GMTSimulated annealing is a polynomial-time approximation scheme for the minimum spanning tree problem
https://scholar.archive.org/work/zto7gwallngpfn4n6pkqdxnxnm
We prove that Simulated Annealing with an appropriate cooling schedule computes arbitrarily tight constant-factor approximations to the minimum spanning tree problem in polynomial time. This result was conjectured by Wegener (2005) . More precisely, denoting by 𝑛, 𝑚, 𝑤 max , and 𝑤 min the number of vertices and edges as well as the maximum and minimum edge weight of the MST instance, we prove that simulated annealing with initial temperature 𝑇 0 ≥ 𝑤 max and multiplicative cooling schedule with factor 1 − 1/ℓ, where ℓ = 𝜔 (𝑚𝑛 ln(𝑚)), with probability at least 1 − 1/𝑚 computes in time 𝑂 (ℓ (ln ln(ℓ) + ln(𝑇 0 /𝑤 min ))) a spanning tree with weight at most 1 + 𝜅 times the optimum weight, where 1 + 𝜅 = (1+𝑜 (1)) ln(ℓ𝑚) ln(ℓ)−ln(𝑚𝑛 ln(𝑚)) . Consequently, for any 𝜀 > 0, we can choose ℓ in such a way that a (1 + 𝜀)-approximation is found in time 𝑂 ((𝑚𝑛 ln(𝑛)) 1+1/𝜀+𝑜 (1) (ln ln 𝑛 + ln(𝑇 0 /𝑤 min ))) with probability at least 1 − 1/𝑚. In the special case of so-called (1 + 𝜀)-separated weights, this algorithm computes an optimal solution (again in time 𝑂 ((𝑚𝑛 ln(𝑛)) 1+1/𝜀+𝑜 (1) (ln ln 𝑛 + ln(𝑇 0 /𝑤 min )))), which is a significant speed-up over Wegener's runtime guarantee of 𝑂 (𝑚 8+8/𝜀 ). CCS CONCEPTS • Theory of computation → Theory of randomized search heuristics.Benjamin Doerr, Amirhossein Rajabi, Carsten Wittwork_zto7gwallngpfn4n6pkqdxnxnmFri, 08 Jul 2022 00:00:00 GMTUnbiasing and robustifying implied volatility calibration in a cryptocurrency market with large bid-ask spreads and missing quotes
https://scholar.archive.org/work/c7y5ht7rq5bsnbrvmmvsrfsivm
We design a novel calibration procedure that is designed to handle the specific characteristics of options on cryptocurrency markets, namely large bid-ask spreads and the possibility of missing or incoherent prices in the considered data sets. We show that this calibration procedure is significantly more robust and accurate than the standard one based on trade and mid-prices.Mnacho Echenim, Emmanuel Gobet, Anne-Claire Mauricework_c7y5ht7rq5bsnbrvmmvsrfsivmWed, 06 Jul 2022 00:00:00 GMTSubexponential Parameterized Algorithms for Cut and Cycle Hitting Problems on H-Minor-Free Graphs
https://scholar.archive.org/work/5ealjkbcerh2titoxqrtbehdqi
We design the first subexponential-time (parameterized) algorithms for several cut and cycle-hitting problems on H-minor free graphs. In particular, we obtain the following results (where k is the solution-size parameter). 1. 2^O(√(k)log k)· n^O(1) time algorithms for Edge Bipartization and Odd Cycle Transversal; 2. a 2^O(√(k)log^4 k)· n^O(1) time algorithm for Edge Multiway Cut and a 2^O(r √(k)log k)· n^O(1) time algorithm for Vertex Multiway Cut, where r is the number of terminals to be separated; 3. a 2^O((r+√(k))log^4 (rk))· n^O(1) time algorithm for Edge Multicut and a 2^O((√(rk)+r) log (rk))· n^O(1) time algorithm for Vertex Multicut, where r is the number of terminal pairs to be separated; 4. a 2^O(√(k)log g log^4 k)· n^O(1) time algorithm for Group Feedback Edge Set and a 2^O(g √(k)log(gk))· n^O(1) time algorithm for Group Feedback Vertex Set, where g is the size of the group. 5. In addition, our approach also gives n^O(√(k)) time algorithms for all above problems with the exception of n^O(r+√(k)) time for Edge/Vertex Multicut and (ng)^O(√(k)) time for Group Feedback Edge/Vertex Set. We obtain our results by giving a new decomposition theorem on graphs of bounded genus, or more generally, an h-almost-embeddable graph for any fixed constant h. In particular we show the following. Let G be an h-almost-embeddable graph for a constant h. Then for every p∈ℕ, there exist disjoint sets Z_1,...,Z_p ⊆ V(G) such that for every i ∈{1,...,p} and every Z'⊆ Z_i, the treewidth of G/(Z_i\ Z') is O(p+|Z'|). Here G/(Z_i\ Z') is the graph obtained from G by contracting edges with both endpoints in Z_i \ Z'.Sayan Bandyapadhyay, William Lochet, Daniel Lokshtanov, Saket Saurabh, Jie Xuework_5ealjkbcerh2titoxqrtbehdqiMon, 04 Jul 2022 00:00:00 GMTCommunity Recovery in the Geometric Block Model
https://scholar.archive.org/work/vqkwe5n7gneqvcynhj5qeqeyce
To capture inherent geometric features of many community detection problems, we propose to use a new random graph model of communities that we call a Geometric Block Model. The geometric block model builds on the random geometric graphs (Gilbert, 1961), one of the basic models of random graphs for spatial networks, in the same way that the well-studied stochastic block model builds on the Erdős-Réńyi random graphs. It is also a natural extension of random community models inspired by the recent theoretical and practical advancements in community detection. To analyze the geometric block model, we first provide new connectivity results for random annulus graphs which are generalizations of random geometric graphs. The connectivity properties of geometric graphs have been studied since their introduction, and analyzing them has been difficult due to correlated edge formation. We then use the connectivity results of random annulus graphs to provide necessary and sufficient conditions for efficient recovery of communities for the geometric block model. We show that a simple triangle-counting algorithm to detect communities in the geometric block model is near-optimal. For this we consider two regimes of graph density. In the regime where the average degree of the graph grows logarithmically with number of vertices, we show that our algorithm performs extremely well, both theoretically and practically. In contrast, the triangle-counting algorithm is far from being optimum for the stochastic block model in the logarithmic degree regime. We also look at the regime where the average degree of the graph grows linearly with the number of vertices n, and hence to store the graph one needs Θ(n^2) memory. We show that our algorithm needs to store only O(n log n) edges in this regime to recover the latent communities.Sainyam Galhotra, Arya Mazumdar, Soumyabrata Pal, Barna Sahawork_vqkwe5n7gneqvcynhj5qeqeyceWed, 22 Jun 2022 00:00:00 GMTMaternal age affects equine day 8 embryo gene expression both in trophoblast and inner cell mass
https://scholar.archive.org/work/wdx74vjzl5c35nlpj3zfzbg7pu
Background Breeding a mare until she is not fertile or even until her death is common in equine industry but the fertility decreases as the mare age increases. Embryo loss due to reduced embryo quality is partly accountable for this observation. Here, the effect of mare's age on blastocysts' gene expression was explored. Day 8 post-ovulation embryos were collected from multiparous young (YM, 6-year-old, N = 5) and older (OM, > 10-year-old, N = 6) non-nursing Saddlebred mares, inseminated with the semen of one stallion. Pure or inner cell mass (ICM) enriched trophoblast, obtained by embryo bisection, were RNA sequenced. Deconvolution algorithm was used to discriminate gene expression in the ICM from that in the trophoblast. Differential expression was analyzed with embryo sex and diameter as cofactors. Functional annotation and classification of differentially expressed genes and gene set enrichment analysis were also performed. Results Maternal aging did not affect embryo recovery rate, embryo diameter nor total RNA quantity. In both compartments, the expression of genes involved in mitochondria and protein metabolism were disturbed by maternal age, although more genes were affected in the ICM. Mitosis, signaling and adhesion pathways and embryo development were decreased in the ICM of embryos from old mares. In trophoblast, ion movement pathways were affected. Conclusions This is the first study showing that maternal age affects gene expression in the equine blastocyst, demonstrating significant effects as early as 10 years of age. These perturbations may affect further embryo development and contribute to decreased fertility due to aging.Emilie Derisoud, Luc Jouneau, Cédric Dubois, Catherine Archilla, Yan Jaszczyszyn, Rachel Legendre, Nathalie Daniel, Nathalie Peynot, Michèle Dahirel, Juliette Auclair-Ronzaud, Laurence Wimel, Véronique Duranthon, Pascale Chavatte-Palmerwork_wdx74vjzl5c35nlpj3zfzbg7puWed, 15 Jun 2022 00:00:00 GMTLanthanide-based single-molecule magnets: A rational design by chemical intuition
https://scholar.archive.org/work/otyupgayxzcnzmmx5vkwm3u76y
A model complex of dysprosium, Dy(N2O2C7H11)3 (Dy2) was built by successive capping of the peripheral aromatic ring of a butterfly-shaped dysprosium complex of a schiff base ligand, Dy(N4O5C14H11)3 (Dy1). The structural modifications were carried out in order to investigate the effect of the chemical surroundings like aromaticity on the observation of single-molecule magnet (SMM) behaviour in a lanthanide-based complex (Dy1). Experimental techniques were combined with theoretical tools to investigate the dynamics of magnetic properties of the Dy1 and compared with the theoretical results for Dy2 to gain insight on the contribution of covalency, crystal field effect and the role of aromaticity in stabilizing the excited magnetic levels of a single-molecule magnet. Dy1 showed frequency-dependent slow magnetic relaxation characteristics of a single-molecule magnet with and without applied dc field and a blocking temperature of about 8 K. The obtained results showed that despite f−electrons having weak interactions with ligand field, it is possible to tune the magnetic properties of lanthanide-based complexes using ring currents, control of covalency and peripheral ligand substitution. Furthermore, di-nuclear acetate bridged lanthanide complexes with two different structural motifs, Er1 = [Er(CH3COO)(CH3COO)2(H2O)2]2 · 4H2O and [Ln(CH3COO)(CH3COO)(CH3COO)(H2O)CH3COOH]2 · 2CH3COOH (Ln = Er (Er2), Y0.8Er0.2 (Er3)) were characterised. The solvent effects on the structure, electronic and magnetic properties were studied by experiments and theoretical methods. The tetraacetate-bridged erbium (Er2) showed a shorter intra-molecular Er – Er distance of 3.878 Å compared to the doubly-bridged counterpart (Er1) with Er – Er intra-molecular separation of 4.152 Å. Er2 exhibited weak ferromagnetic ordering at very low temperature in the dc magnetic measurement due to the short proximity of the Er centres. A field-induced slow magnetic relaxation for spin reversal characteristics of single-molecule magnet behaviour with relaxation [...]David Izuogu, Apollo-University Of Cambridge Repository, Alexander JW Thomwork_otyupgayxzcnzmmx5vkwm3u76yMon, 30 May 2022 00:00:00 GMTNotch controls the cell cycle to define leader versus follower identities during collective cell migration
https://scholar.archive.org/work/it2etiyrz5dqvknrsngu7cn7fq
Coordination of cell proliferation and migration is fundamental for life, and its dysregulation has catastrophic consequences, such as cancer. How cell cycle progression affects migration, and vice-versa, remains largely unknown. We address these questions by combining in-silico modelling and in vivo experimentation in the zebrafish Trunk Neural Crest (TNC). TNC migrate collectively, forming chains with a leader cell directing the movement of trailing followers. We show that the acquisition of migratory identity is autonomously controlled by Notch signalling in TNC. High Notch activity defines leaders, while low Notch determines followers. Moreover, cell cycle progression is required for TNC migration and is regulated by Notch. Cells with low Notch activity stay longer in G1 and become followers, while leaders with high Notch activity quickly undergo G1/S transition and remain in S-phase longer. In conclusion, TNC migratory identities are defined through the interaction of Notch signalling and cell cycle progression.Zain Alhashem, Dylan Feldner-Busztin, Christopher Revell, Macarena Alvarez-Garcillan Portillo, Karen Camargo-Sosa, Joanna Richardson, Manuel Rocha, Anton Gauert, Tatianna Corbeaux, Martina Milanetto, Francesco Argenton, Natascia Tiso, Robert N Kelsh, Victoria E Prince, Katie Bentley, Claudia Linkerwork_it2etiyrz5dqvknrsngu7cn7fqThu, 26 May 2022 00:00:00 GMT