Time Hypothesis Research Articles

Approximately Counting Answers to Conjunctive Queries with Disequalities and Negations

We study the complexity of approximating the number of answers to a small query \(\varphi\) in a large database \(\mathcal{D}\) . We establish an exhaustive classification into tractable and intractable cases if \(\varphi\) is a conjunctive query possibly including disequalities and negations: — If there is a constant bound on the arity of \(\varphi\) , and if the randomised Exponential Time Hypothesis (rETH) holds, then the problem has a fixed-parameter tractable approximation scheme (FPTRAS) if and only if the treewidth of \(\varphi\) is bounded. — If the arity is unbounded and \(\varphi\) does not have negations, then the problem has an FPTRAS if and only if the adaptive width of \(\varphi\) (a width measure strictly more general than treewidth) is bounded; the lower bound relies on the rETH as well. Additionally we show that our results cannot be strengthened to achieve a fully polynomial randomised approximation scheme (FPRAS): We observe that, unless \(\mathrm{NP}=\mathrm{RP}\) , there is no FPRAS even if the treewidth (and the adaptive width) is \(1\) . However, if there are neither disequalities nor negations, we prove the existence of an FPRAS for queries of bounded fractional hypertreewidth, strictly generalising the recently established FPRAS for conjunctive queries with bounded hypertreewidth due to Arenas, Croquevielle, Jayaram and Riveros (STOC 2021).

Intermittent or Continuous Panitumumab Plus Fluorouracil, Leucovorin, and Irinotecan for First-Line Treatment of RAS and BRAF Wild-Type Metastatic Colorectal Cancer: The IMPROVE Trial.

To investigate whether intermittent treatment after an induction phase of first-line schedule of fluorouracil, leucovorin, and irinotecan (FOLFIRI) plus panitumumab (PAN) prevents or delays the onset of resistance and improves safety and compliance with treatment in patients with unresectable RAS/BRAF wild-type (wt) metastatic colorectal cancer (mCRC). IMPROVE (ClinicalTrials.gov identifier: NCT04425239) was an open-label, multicenter, randomized phase II noncomparative trial. Patients with unresectable RAS/BRAF wt mCRC were randomly assigned (1:1) to receive FOLFIRI plus PAN continuously until progression (arm A) or intermittently, with treatment-free intervals (arm B) until progression on treatment, toxicity, or death. The primary end point was progression-free survival on treatment (PFSot) at 12 months. Assuming a null hypothesis of median PFSot time ≤7 months and target PFSot ≥10 months, 65 patients per arm were needed to achieve 80% power and 10% type I error, according to the binomial test. Between May 2018 and June 2021, 69 patients were randomly assigned to arm A and 68 to arm B. The median number of treatment cycles was 13 in arm A and 16 in arm B. At a median follow-up of 43.2 months (IQR, 35.0-50.5), median PFSot was 11.2 and 17.5 months with 12-month PFSot rates of 45.7% and 58.5%, for arms A and B, respectively. The overall response rates were 68.1% and 61.2%, and median overall survival rates were 36.3 and 35.1 months in arms A and B, respectively. The overall rate of grade >2 skin PAN-related adverse events was 30.3% in arm A and 17.9% in arm B. Intermittent FOLFIRI plus PAN after the induction phase was feasible, and the primary end point was met with reduced toxicity while allowing patients more time off treatment.

Hardness of Approximate Diameter: Now for Undirected Graphs

Approximating the graph diameter is a basic task of both theoretical and practical interest. A simple folklore algorithm can output a 2-approximation to the diameter in linear time by running BFS from an arbitrary vertex. It has been open whether a better approximation is possible in near-linear time. A series of papers on fine-grained complexity have led to strong hardness results for diameter in directed graphs, culminating in a recent tradeoff curve independently discovered by [Li, STOC’21] and [Dalirrooyfard and Wein, STOC’21], showing that under the Strong Exponential Time Hypothesis (SETH), for any integer k ≥ 2 and δ > 0, a \(2-\frac{1}{k}-\delta \) approximation for diameter in directed m -edge graphs requires m 1 + 1/( k − 1) − o (1) time. In particular, the simple linear time 2-approximation algorithm is optimal for directed graphs. In this paper we prove that the same tradeoff lower bound curve is possible for undirected graphs as well, extending results of [Roditty and Vassilevska W., STOC’13], [Li’20] and [Bonnet, ICALP’21] who proved the first few cases of the curve, k = 2, 3 and 4, respectively. Our result shows in particular that the simple linear time 2-approximation algorithm is also optimal for undirected graphs. To obtain our result, we extract the core ideas in known reductions and introduce a unification and generalization that could be useful for proving SETH-based hardness for other problems in undirected graphs related to distance computation.

Sensitive periods and other timing hypotheses in developmental psychopathology: A tutorial

Abstract Researchers often aim to assess whether repeated measures of an exposure are associated with repeated measures of an outcome. A question of particular interest is how associations between exposures and outcomes may differ over time. In other words, researchers may seek the best form of a temporal model. While several models are possible, researchers often consider a few key models. For example, researchers may hypothesize that an exposure measured during a sensitive period may be associated with repeated measures of the outcome over time. Alternatively, they may hypothesize that the exposure measured immediately before the current time period may be most strongly associated with the outcome at the current time. Finally, they may hypothesize that all prior exposures are important. Many analytic methods cannot compare and evaluate these alternative temporal models, perhaps because they make the restrictive assumption that the associations between exposures and outcomes remains constant over time. Instead, we provide a tutorial describing four temporal models that allow the associations between repeated measures of exposures and outcomes to vary, and showing how to test which temporal model is best supported by the data. By finding the best temporal model, developmental psychopathology researchers can find optimal windows for intervention.

Application of Historical Comprehensive Multimodal Transportation Data for Testing the Commuting Time Paradox: Evidence from the Portland, OR Region

There have been numerous theoretical and empirical transportation studies contesting the stability of commuting time over time. The constant commuting time hypothesis posits that people adjust trip durations, shift across modes, and sort through locations, so that their average commuting time remains within a constant budget. There is a discrepancy between studies applying aggregate analysis and those using disaggregate analysis, and differences in data collection may have contributed to the varying conclusions reported in the literature. This study conducts both aggregate and disaggregate analyses with two travel surveys of the Portland region. We employ descriptive analysis and t-tests to compare the aggregate commuting times of two years and use regression models to explore factors affecting the disaggregate commuting time at the individual trip level to examine whether the stability of the commuting time remains after substantial changes in the transportation and land use systems. Our study indicates that the average commuting time, along with the average commuting distance, increased slightly, as the mode share shifted away from driving during the examined period. The growth in shares of non-driving modes, which are slower than driving, coupled with an increased travel distance, contributed to the small increase in the average commuting time. Our analysis also indicates that the average travel speed improved for transit riders as well as drivers, contradicting earlier research that claims that public transit investment has worsened the congestion in Portland.

Algorithms for subgraph complementation to some classes of graphs

For a class G of graphs, the objective of Subgraph Complementation toG is to find whether there exists a subset S of vertices of the input graph G such that modifying G by complementing the subgraph induced by S results in a graph in G. We obtain a polynomial-time algorithm for the problem when G is the class of graphs with minimum degree at least k, for a constant k, answering an open problem by Fomin et al. (Algorithmica, 2020). When G is the class of graphs without any induced copies of the star graph on t+1 vertices (for any constant t≥3) and diamond, we obtain a polynomial-time algorithm for the problem. This is in contrast with a result by Antony et al. (Algorithmica, 2022) that the problem is NP-complete and cannot be solved in subexponential-time (assuming the Exponential Time Hypothesis) when G is the class of graphs without any induced copies of the star graph on t+1 vertices, for every constant t≥5.

Haplotype-aware sequence alignment to pangenome graphs.

Modern pangenome graphs are built using haplotype-resolved genome assemblies. When mapping reads to a pangenome graph, prioritizing alignments that are consistent with the known haplotypes improves genotyping accuracy. However, the existing rigorous formulations for colinear chaining and alignment problems do not consider the haplotype paths in a pangenome graph. This often leads to spurious read alignments to those paths that are unlikely recombinations of the known haplotypes. In this paper, we develop novel formulations and algorithms for sequence-to-graph alignment and chaining problems. Inspired by the genotype imputation models, we assume that a query sequence is an imperfect mosaic of reference haplotypes. Accordingly, we introduce a recombination penalty in the scoring functions for each haplotype switch. First, we solve haplotype-aware sequence-to-graph alignment in [Formula: see text] time, where Q is the query sequence, E is the set of edges, and H is the set of haplotypes represented in the graph. To complement our solution, we prove that an algorithm significantly faster than [Formula: see text] is impossible under the strong exponential time hypothesis (SETH). Second, we propose a haplotype-aware chaining algorithm that runs in [Formula: see text] time after graph preprocessing, where N is the count of input anchors. We then establish that a chaining algorithm significantly faster than [Formula: see text] is impossible under SETH. As a proof-of-concept, we implemented our chaining algorithm in the Minichain aligner. By aligning sequences sampled from the human major histocompatibility complex (MHC) to a pangenome graph of 60 MHC haplotypes, we demonstrate that our algorithm achieves better consistency with ground-truth recombinations compared with a haplotype-agnostic algorithm.

Counting Complexity for Reasoning in Abstract Argumentation

In this paper, we consider counting and projected model counting of extensions in abstract argumentation for various semantics, including credulous reasoning. When asking for projected counts, we are interested in counting the number of extensions of a given argumentation framework, while multiple extensions that are identical when restricted to the projected arguments count as only one projected extension. We establish classical complexity results and parameterized complexity results when the problems are parameterized by the treewidth of the undirected argumentation graph. To obtain upper bounds for counting projected extensions, we introduce novel algorithms that exploit small treewidth of the undirected argumentation graph of the input instance by dynamic programming. Our algorithms run in double or triple exponential time in the treewidth, depending on the semantics under consideration. Finally, we establish lower bounds of bounded treewidth algorithms for counting extensions and projected extension under the exponential time hypothesis (ETH).

Simulation of RC5 Algorithm to Provide Security for WLAN, Peer-to-Peer

Information security is a significant viewpoint in different areas of correspondence. This paper manages information encryption as large numbers of data correspondence rely upon encryption information. In this paper, another proposition of an information encryption framework has been presented. The framework can be partitioned into two stages; the primary stage centers around creating a top-notch Pseudo Irregular Number generator PRNGs utilizing rudimentary, intermittent, and crossover rules of cell automata CA. The framework recommends another mix of CA rules in an undertaking to give high arbitrariness and to work on the strength of the proposed cryptosystem. The subsequent stage creates the Improved Rivest Code 5 ERC5 calculations which utilizes the produced arbitrary Number Succession RNS with an end goal to reinforce the security and haphazardness of the first Rivest Code 5 RC5 Algorithm. The outcomes show that the proposed PRNGs in light of CA can create RNS with a high period which can reach more than 100000 keys without reiteration or string duplication. In addition, the test exhibits that the proposed ERC5 works on the security of the first RC5 calculation. The proposed cryptosystem is assessed as far as Shannon's hypothesis of data entropy, irregularity tests, calculation time, and key space investigation. The outcomes confirm that the recommended information crypto-framework expands the development of the security level of unique RC5 encryption calculation with a serious level of arbitrariness and privacy. It is executed this work to show the results rely upon the programming language C# and the correspondence was presented in a structure called disseminated through an association wireless local-area network WIFI.

Capital Structure Dynamics: Evidence from the Korean Listing Market

This study analyzes how the trade-off theory, capital financing priority theory, and market timing hypothesis impact corporate capital structure for sustainable growth. Using a panel regression and system generalized method for moment analyses with balanced panel data for 1636 listed firms in the Korean stock market and KOSDAQ from 2011 to 2021, we discovered that the level of and change in capital structure are determined through a complex mechanism in which the target debt ratio adjustment speed, previous year’s debt ratio, target debt ratio divergence, funding shortage situation, and market timing hypothesis interact complementarily. This indicates that the capital structure decisions of Korean listed firms are characterized by a complex mechanism that is difficult to explain with a single theory. The findings of this study have practical implications for understanding the capital structure decisions of Korean firms and for designing efficient capital-raising strategies. Additionally, by revealing the complementary relationship between the two theories, this study provides directions for future research on corporate capital structure.

The Fine-Grained Complexity of Graph Homomorphism Parameterized by Clique-Width

The generic homomorphism problem, which asks whether an input graph \(G\) admits a homomorphism into a fixed target graph \(H\) , has been widely studied in the literature. In this article, we provide a fine-grained complexity classification of the running time of the homomorphism problem with respect to the clique-width of \(G\) (denoted \({\operatorname{cw}}\) ) for virtually all choices of \(H\) under the Strong Exponential Time Hypothesis. In particular, we identify a property of \(H\) called the signature number \(s(H)\) and show that for each \(H\) , the homomorphism problem can be solved in time \(\mathcal{O^{*}}(s(H)^{{\operatorname{cw}}})\) . Crucially, we then show that this algorithm can be used to obtain essentially tight upper bounds. Specifically, we provide a reduction that yields matching lower bounds for each \(H\) that is either a projective core or a graph admitting a factorization with additional properties—allowing us to cover all possible target graphs under long-standing conjectures.

On conflict-free cuts: Algorithms and complexity

One way to define the Matching Cut problem is: Given a graph G, is there an edge-cut M of G such that M is an independent set in the line graph of G? We propose the more general Conflict-Free Cut problem: Together with the graph G, we are given a so-called conflict graph Gˆ on the edges of G, and we ask for an edge-cutset M of G that is independent in Gˆ. Since conflict-free settings are popular generalizations of classical optimization problems and Conflict-Free Cut was not considered in the literature so far, we start the study of the problem. We show that the problem is NP-complete even when the maximum degree of G is 5 and Gˆ is 1-regular. The same reduction implies an exponential lower bound on the solvability based on the Exponential Time Hypothesis. We also give parameterized complexity results: We show that the problem is fixed-parameter tractable with the vertex cover number of G as a parameter, and we show W[1]-hardness even when G has a feedback vertex set of size one, and the clique cover number of Gˆ is the parameter. Since the clique cover number of Gˆ is an upper bound on the independence number of Gˆ and thus the solution size, this implies W[1]-hardness when parameterized by the cut size. We list polynomial-time solvable cases and interesting open problems. At last, we draw a connection to a symmetric variant of SAT.

The parameterized complexity of finding minimum bounded chains

Finding the smallest d-chain with a specific (d−1)-boundary in a simplicial complex is known as the Minimum Bounded Chain problem (MBCd). MBCd is NP-hard for all d≥2. In this paper, we prove that it is also W[1]-hard for all d≥2, if we parameterize the problem by solution size. We also give an algorithm solving MBC1 in polynomial time and introduce and implement two fixed parameter tractable (FPT) algorithms solving MBCd for all d. The first algorithm uses a shortest path approach and is parameterized by solution size and coface degree. The second algorithm is a dynamic programming approach based on treewidth, which has the same runtime as a lower bound we prove under the exponential time hypothesis.

The grammaticalization of the existential sign var in Turkish Sign Language: a Construction Grammar approach

Abstract This paper describes the development of the existential sign var ‘there’ in Turkish Sign Language from a synchronic point of view. The sign has been previously described as being restricted to clause-final predicate position and typically used for two main linguistic functions: (i) existential and (ii) possessive. However, abundant corpus evidence indicates that var can also be used for other linguistic functions in post-verbal position, which have not been reported in the literature before. Following Construction Grammar, this study presents a theoretical framework to investigate how the construction [verb + var] arose and what its semantic motivation is, paying particular attention to the notion of possession. It is argued that this construction has three different functions: (i) habitual, (ii) evidential, and (iii) assumptive. According to this account, var originated as an existential marker and subsequently developed into a marker of possession, before evolving to encompass its other linguistic functions in three stages. Using Labov’s Apparent Time Hypothesis (Labov, William. 1963. The social motivation of a sound change. Word 19(3). 273–309), closer examination also revealed that a progressive difference exists between age groups. Younger TİD signers use the construction [verb + var] more frequently, and as the age of the TİD signer decreases, the usage of this construction in the assumptive function increases considerably.

Effect of Private Sector Credit on Economic Growth in Nepal

This study aims to examine the key economic indicators with private sector credit and economic growth in Nepal. Commercial banks and other financial institutions lend money to businesses and individuals for investment and consumption. This study aims to analyze key economic indicators in Nepal, including Real Gross Domestic Product (RGDP), Private Sector Credit (PSC), and Gross Capital Formation (GCF), spanning from 1975 to 2022. Employing a quantitative methodology, econometric techniques such as time series analysis, regression modeling, and hypothesis testing were utilized to examine the long-term relationships among these variables, with a particular focus on the impact of Private Sector Credit on Economic Growth (EG). The findings, derived from comprehensive econometric analyses including co-integration tests and vector error correction models, reveal significant insights into Nepal’s economic performance and financial system. Results indicate that Private Sector Credit plays a crucial role in stimulating economic growth, with approximately 40.07% of the previous year’s imbalance influenced by the long-term elasticity of independent variables. These findings offer valuable insights for policymakers, businesses, and investors, facilitating informed decision-making to promote sustainable economic development in Nepal. Further research is recommended to explore the correlation between the diversification of Private Sector Credit types and economic growth more comprehensively.

Lagrangian and Eulerian modelling of 106Ru atmospheric transport in 2017 over northern hemisphere

In September 2017, numerous measurement stations recorded large surface concentrations of Ru106 in Europe. This event was well recorded by various monitoring stations worldwide and offer a valuable framework to compare the modelling strategies deployed to quickly evaluate where the plume goes and with what concentrations. In general, the source and its intensity are not known and hypotheses have to be done. Models have to be fast and accurate: Lagrangian and Eulerian are often used but rarely compared. In this study, the FLEXPART Lagrangian model and the WRF-CHIMERE Eulerian models are used to simulate the emissions, transport and deposition of this source of Ru106. First, it is shown that the hypothesis of location, timing and intensity of the source is realistic, by comparison to surface measurements. Second, sensitivity analysis performed with the Eulerian model and several transport scheme showed that this model may provide better results than the Lagrangian one. It opens the door to further development, including chemistry and mixing with other pollutants during these specific events.

A Two-Dimensional Time to Reconcile Quantum Theory and General Relativity

Currently, modern physics considers space-time in 4 dimensions (3 spatial, and 1 temporal) and is facing the problem of unifying the two major theories: quantum theory and general relativity. To circumvent the obstacles to this unification, we propose to think of a space with 5 Dimensions (3 spatial, 2 temporal). We thus make the hypothesis of a decomposable time in a two-dimensional orthonormal space, just like a distance is decomposable in a 3-dimensional space: First Dimension: The classical time T that we know, that of mass in the sense of intuitive perception, but in fact that of matter, or “corpuscular” time and therefore our reference time in our perceived reality. In our thought experiment, this will be the time T of the macroscopic observer (Thought Experiment)

Tip dating and Bayes factors provide insight into the divergences of crown bird clades across the end-Cretaceous mass extinction.

The origin of crown birds (Neornithes) remains contentious owing to conflicting divergence time hypotheses obtained from alternative sources of data. The fossil record suggests limited diversification of Neornithes in the Late Mesozoic and a substantial radiation in the aftermath of the Cretaceous-Palaeogene (K-Pg) mass extinction, approximately 66 Ma. Molecular clock studies, however, have yielded estimates for neornithine origins ranging from the Early Cretaceous (130 Ma) to less than 10 Myr before the K-Pg. We use Bayes factors to compare the fit of node ages from different molecular clock studies to an independent morphological dataset. Our results allow us to reject scenarios of crown bird origins deep in the Early Cretaceous, as well as an origin of crown birds within the last 10 Myr of the Cretaceous. The scenario best supported by our analyses is one where Neornithes originated between the Early and Late Cretaceous (ca 100 Ma), while numerous divergences within major neoavian clades either span or postdate the K-Pg. This study affirms the importance of the K-Pg on the diversification of modern birds, and the potential of combined-evidence tip-dating analyses to illuminate recalcitrant 'rocks versus clocks' debates.

A web-based geovisualization framework for exploratory analysis of individual VGI contributor’s participation characteristics

ABSTRACT Understanding the participation characteristics of VGI (volunteered geographic information) contributors is important as their active participation and consistent data contribution are key to success of any VGI project. Existing studies on this matter focused primarily on deriving and interpreting participation patterns of contributor groups. There is a lack of investigation into the participation pattern of individual contributors, which can be complementary to a comprehensive understanding of VGI contributors’ participation characteristics. Building and using a custom web-based geovisualization framework, this study explores the individual-level participation characteristics of VGI contributors from the perspectives of spatial, temporal, thematic, and social interaction patterns. I conducted geovisual exploratory data analysis on VGI datasets from the iNaturalist biodiversity citizen science project to gain intuitions on the clustering and variabilities of participation patterns in iNaturalist, detect participation pattern shifts over time and form explanation hypotheses, and assess and develop metrics to measure participation. The geovisualization framework is expected to be generally applicable to other VGI datasets for exploring individual-level contributor participation patterns. This work is among the first efforts to explore individual-level VGI participation characteristics through geovisualization and geovisual analytics.

Safe sets and in-dominating sets in digraphs

A non-empty subset S of the vertices of a digraph D is a safe set if(i) for every strongly connected component M of D−S, there exists a strongly connected component N of D[S] such that there exists an arc from M to N; and(ii) for every strongly connected component M of D−S and every strongly connected component N of D[S], we have |M|≤|N| whenever there exists an arc from M to N.In the case of acyclic digraphs a set X of vertices is a safe set precisely when X is an in-dominating set, that is, every vertex not in X has at least one arc to X. We prove that, even for acyclic digraphs which are traceable (have a hamiltonian path) it is NP-hard to find a minimum cardinality safe (in-dominating) set. Then we show that the problem is also NP-hard for tournaments and give, for every positive constant c, a polynomial algorithm for finding a minimum cardinality safe set in a tournament on n vertices in which no strong component has size more than clog(n). Under the so called Exponential Time Hypothesis (ETH) this is close to best possible in the following sense: If ETH holds, then, for every ϵ>0 there is no polynomial time algorithm for finding a minimum cardinality safe set for the class of tournaments in which the largest strong component has size at most log1+ϵ(n). We also discuss bounds on the cardinality of safe sets in tournaments.