Conditional Lower Bounds for Space/Time Tradeoffs

In recent years much effort has been concentrated towards achieving polynomial time lower bounds on algorithms for solving various well-known problems. A useful technique for showing such lower bounds is to prove them conditionally based on well-studied hardness assumptions such as 3SUM, APSP, SETH, etc. This line of research helps to obtain a better understanding of the complexity inside P. A related question asks to prove conditional space lower bounds on data structures that are constructed to solve certain algorithmic tasks after an initial preprocessing stage. This question received little attention in previous research even though it has potential strong impact. In this paper we address this question and show that surprisingly many of the well-studied hard problems that are known to have conditional polynomial time lower bounds are also hard when concerning space. This hardness is shown as a tradeoff between the space consumed by the data structure and the time needed to answer queries. The tradeoff may be either smooth or admit one or more singularity points. We reveal interesting connections between different space hardness conjectures and present matching upper bounds. We also apply these hardness conjectures to both static and dynamic problems and prove their conditional space hardness. We believe that this novel framework of polynomial space conjectures can play an important role in expressing polynomial space lower bounds of many important algorithmic problems. Moreover, it seems that it can also help in achieving a better understanding of the hardness of their corresponding problems in terms of time

Immunodiagnosis of Trichinella infection in the horse.

From 1998 to 2000, 5,267 horse sera were collected from several Trichinella regions in Romania. Sera were initially screened in laboratories in Romania, Serbia and Italy with an ELISA and a Western blot (Wb) using an excretory/secretory (ES) antigen and several conjugates (protein A, protein G, and sheep or goat anti-horse). Differences in serology results were obtained among the different conjugates and also between ELISA and Wb. Depending on the test used, specific antibodies were found at a prevalence rate of 3-6 % of horses. Serum samples classified as positive were tested again by ELISA using a synthetic tyvelose glycan-BSA antigen, in Italy. All serum samples tested using this antigen were negative; in contrast, serum samples from experimentally infected horses were positive with the glycan antigen. The negative results obtained with the glycan antigen are consistent with the low prevalence of horse trichinellosis reported in the literature. Based on these results, further studies are needed to validate immunodiagnostic tests to detect Trichinella infection in horses

Hardness of Approximate Nearest Neighbor Search

We prove conditional near-quadratic running time lower bounds for approximate Bichromatic Closest Pair with Euclidean, Manhattan, Hamming, or edit distance. Specifically, unless the Strong Exponential Time Hypothesis (SETH) is false, for every $\delta>0$ there exists a constant $\epsilon>0$ such that computing a $(1+\epsilon)$-approximation to the Bichromatic Closest Pair requires $n^{2-\delta}$ time. In particular, this implies a near-linear query time for Approximate Nearest Neighbor search with polynomial preprocessing time. Our reduction uses the Distributed PCP framework of [ARW'17], but obtains improved efficiency using Algebraic Geometry (AG) codes. Efficient PCPs from AG codes have been constructed in other settings before [BKKMS'16, BCGRS'17], but our construction is the first to yield new hardness results

Graphs Cannot Be Indexed in Polynomial Time for Sub-quadratic Time String Matching, Unless SETH Fails

The string matching problem on a node-labeled graph G= (V, E) asks whether a given pattern string P has an occurrence in G, in the form of a path whose concatenation of node labels equals P. This is a basic primitive in various problems in bioinformatics, graph databases, or networks, but only recently proven to have a O(|E||P|)-time lower bound, under the Orthogonal Vectors Hypothesis (OVH). We consider here its indexed version, in which we can index the graph in order to support time-efficient string queries. We show that, under OVH, no polynomial-time indexing scheme of the graph can support querying P in time O(| P| + | E| δ| P| β), with either δ< 1 or β< 1. As a side-contribution, we introduce the notion of linear independent-components (lic) reduction, allowing for a simple proof of our result. As another illustration that hardness of indexing follows as a corollary of a lic reduction, we also translate the quadratic conditional lower bound of Backurs and Indyk (STOC 2015) for the problem of matching a query string inside a text, under edit distance. We obtain an analogous tight quadratic lower bound for its indexed version, improving the recent result of Cohen-Addad, Feuilloley and Starikovskaya (SODA 2019), but with a slightly different boundary condition.Peer reviewe

Prognostic impact of acute pulmonary triggers in patients with takotsubo syndrome: new insights from the International Takotsubo Registry

AIMS Acute pulmonary disorders are known physical triggers of takotsubo syndrome (TTS). This study aimed to investigate prevalence of acute pulmonary triggers in patients with TTS and their impact on outcomes. METHODS AND RESULTS Patients with TTS were enrolled from the International Takotsubo Registry and screened for triggering factors and comorbidities. Patients were categorized into three groups (acute pulmonary trigger, chronic lung disease, and no lung disease) to compare clinical characteristics and outcomes. Of the 1670 included patients with TTS, 123 (7%) were identified with an acute pulmonary trigger, and 194 (12%) had a known history of chronic lung disease. The incidence of cardiogenic shock was highest in patients with an acute pulmonary trigger compared with those with chronic lung disease or without lung disease (17% vs. 10% vs. 9%, P = 0.017). In-hospital mortality was also higher in patients with an acute pulmonary trigger than in the other two groups, although not significantly (5.7% vs. 1.5% vs. 4.2%, P = 0.13). Survival analysis demonstrated that patients with an acute pulmonary trigger had the worst long-term outcome (P = 0.002). The presence of an acute pulmonary trigger was independently associated with worse long-term mortality (hazard ratio 2.12, 95% confidence interval 1.33-3.38; P = 0.002). CONCLUSIONS The present study demonstrates that TTS is related to acute pulmonary triggers in 7% of all TTS patients, which accounts for 21% of patients with physical triggers. The presence of acute pulmonary trigger is associated with a severe in-hospital course and a worse long-term outcome

Research trends in forensic science:A scientometric approach to analyze the content of the INTERPOL reviews

The use of forensic evidence has become indispensable in many countries and jurisdictions around the world, however the dissemination of research advancements does not necessarily directly or easily reach the forensic science community. Reports from the INTERPOL International Forensic Science Managers Symposium outline major areas that are of interest to forensic practitioners across the INTERPOL member countries. The information contained in the INTERPOL reports is extensive but can be challenging to process. The purpose of this research is to provide a comprehensive overview of the evolution of trends within the INTERPOL reports over an 18 year period. References relating to 10 evidence types retrieved from the 14th to 19th INTERPOL IFSMS reports (2004-2019) were processed and compared with data exports from the citation database Scopus covering the same evidence types. The results from this work are summarised by investigating the relationships between the 10 evidence types. To explore the outputs a user-friendly R-Shiny application was developed and is freely available at: https://uod.ac.uk/lrcfsinterpolreportsexplorer

The lateral flow card test: an alternative method for the detection of Trichinella infection in swine

A novel lateral flow card (TS-Card pork) test was developed for the serological detection of Trichinella infected pigs. Based on extensive studies performed in Romania during 1 999-2000 this test proved to be highly specific, sensitive, rapid (3-12 minutes) and easy to use (no need for laboratory facilities). It can be used both for the detection of Trichinella infection in carcasses and for epizootiological studies using a variety of samples including whole or dried blood, serum, or tissue fluids. The TS-Card pork test, used as a screening test, can be the foundation of an on-farm or field based inspection system to significantly improve food safety in countries with a high prevalence of Trichinella in pigs or other food animal species. The results presented are also promising for application of the test in an on-line laboratory based inspection system since the speed of the test allows sufficient time to rail out suspected hog carcasses during the slaughter process