734 research outputs found
Desalination effluents and the establishment of the non-indigenous skeleton shrimp Paracaprella pusilla Mayer, 1890 in the south-eastern Mediterranean
A decade long monitoring programme has revealed a flourishing population of the non-indigenous skeleton shrimp Paracaprella pusilla in the vicinity of outfalls of desalination plants off the Mediterranean coast of Israel. The first specimens were collected in 2010, thus predating all previously published records of this species in the Mediterranean Sea. A decade-long disturbance regime related to the construction and operation of the plants may have had a critical role in driving the population growth
Finding 2-Edge and 2-Vertex Strongly Connected Components in Quadratic Time
We present faster algorithms for computing the 2-edge and 2-vertex strongly
connected components of a directed graph, which are straightforward
generalizations of strongly connected components. While in undirected graphs
the 2-edge and 2-vertex connected components can be found in linear time, in
directed graphs only rather simple -time algorithms were known. We use
a hierarchical sparsification technique to obtain algorithms that run in time
. For 2-edge strongly connected components our algorithm gives the
first running time improvement in 20 years. Additionally we present an -time algorithm for 2-edge strongly connected components, and thus
improve over the running time also when . Our approach
extends to k-edge and k-vertex strongly connected components for any constant k
with a running time of for edges and for vertices
Searching of gapped repeats and subrepetitions in a word
A gapped repeat is a factor of the form where and are nonempty
words. The period of the gapped repeat is defined as . The gapped
repeat is maximal if it cannot be extended to the left or to the right by at
least one letter with preserving its period. The gapped repeat is called
-gapped if its period is not greater than . A
-subrepetition is a factor which exponent is less than 2 but is not
less than (the exponent of the factor is the quotient of the length
and the minimal period of the factor). The -subrepetition is maximal if
it cannot be extended to the left or to the right by at least one letter with
preserving its minimal period. We reveal a close relation between maximal
gapped repeats and maximal subrepetitions. Moreover, we show that in a word of
length the number of maximal -gapped repeats is bounded by
and the number of maximal -subrepetitions is bounded by
. Using the obtained upper bounds, we propose algorithms for
finding all maximal -gapped repeats and all maximal
-subrepetitions in a word of length . The algorithm for finding all
maximal -gapped repeats has time complexity for the case
of constant alphabet size and time complexity for the
general case. For finding all maximal -subrepetitions we propose two
algorithms. The first algorithm has time
complexity for the case of constant alphabet size and time complexity for the general case. The
second algorithm has
expected time complexity
Carotid plaque area: A tool for targeting and evaluating vascular preventive therapy
Background and Purpose - Carotid plaque area measured by ultrasound (cross-sectional area of longitudinal views of all plaques seen) was studied as a way of identifying patients at increased risk of stroke, myocardial infarction, and vascular death. Methods - Patients from an atherosclerosis prevention clinic were followed up annually for up to 5 years (mean, 2.5±1.3 years) with baseline and follow-up measurements recorded. Plaque area progression (or regression) was defined as an increase (or decrease) of ≥0.05 cm2 from baseline. Results - Carotid plaque areas from 1686 patients were categorized into 4 quartile ranges: 0.00 to 0.11 cm2 (n=422), 0.12 to 0.45 cm2 (n=424), 0.46 to 1.18 cm2 (n=421), and 1.19 to 6.73 cm2 (n=419). The combined 5-year risk of stroke, myocardial infarction, and vascular death increased by quartile of plaque area: 5.6%, 10.7%, 13.9%, and 19.5%, respectively (P\u3c0.001) after adjustment for all baseline patient characteristics. A total of 1085 patients had ≥1 annual carotid plaque area measurements: 685 (63.1%) had carotid plaque progression, 306 (28.2%) had plaque regression, and 176 (16.2%) had no change in carotid plaque area over the period of follow-up. The 5-year adjusted risk of combined outcome was 9.4%, 7.6%, and 15.7% for patients with carotid plaque area regression, no change, and progression, respectively (P=0.003). Conclusions - Carotid plaque area and progression of plaque identified high-risk patients. Plaque measurement may be useful for targeting preventive therapy and evaluating new treatments and response to therapy and may improve cost-effectiveness of secondary preventive treatment
Ternary Syndrome Decoding with Large Weight
The Syndrome Decoding problem is at the core of many code-based
cryptosystems. In this paper, we study ternary Syndrome Decoding in large
weight. This problem has been introduced in the Wave signature scheme but has
never been thoroughly studied. We perform an algorithmic study of this problem
which results in an update of the Wave parameters. On a more fundamental level,
we show that ternary Syndrome Decoding with large weight is a really harder
problem than the binary Syndrome Decoding problem, which could have several
applications for the design of code-based cryptosystems
Detecting One-variable Patterns
Given a pattern such that
, where is a
variable and its reversal, and
are strings that contain no variables, we describe an
algorithm that constructs in time a compact representation of all
instances of in an input string of length over a polynomially bounded
integer alphabet, so that one can report those instances in time.Comment: 16 pages (+13 pages of Appendix), 4 figures, accepted to SPIRE 201
Classification of non-indigenous species based on their impacts: Considerations for application in marine management
Assessment of the ecological and economic/societal impacts of the introduction of non-indigenous species (NIS) is one of the primary focus areas of bioinvasion science in terrestrial and aquatic environments, and is considered essential to management. A classification system of NIS, based on the magnitude of their environmental impacts, was recently proposed to assist management. Here, we consider the potential application of this classification scheme to the marine environment, and offer a complementary framework focussing on value sets in order to explicitly address marine management concerns. Since existing data on marine NIS impacts are scarce and successful marine removals are rare, we propose that management of marine NIS adopt a precautionary approach, which not only would emphasise preventing new incursions through pre-border and at-border controls but also should influence the categorisation of impacts. The study of marine invasion impacts requires urgent attention and significant investment, since we lack the luxury of waiting for the knowledge base to be acquired before the window of opportunity closes for feasible management
Online Detection of Repetitions with Backtracking
In this paper we present two algorithms for the following problem: given a
string and a rational , detect in the online fashion the earliest
occurrence of a repetition of exponent in the string.
1. The first algorithm supports the backtrack operation removing the last
letter of the input string. This solution runs in time and
space, where is the maximal length of a string generated during the
execution of a given sequence of read and backtrack operations.
2. The second algorithm works in time and space,
where is the length of the input string and is the number of
distinct letters. This algorithm is relatively simple and requires much less
memory than the previously known solution with the same working time and space.
a string generated during the execution of a given sequence of read and
backtrack operations.Comment: 12 pages, 5 figures, accepted to CPM 201
The enlargement of the Suez Canal and introduction of non-indigenous species to the Mediterranean Sea
The Suez Canal is one of the most important waterways in the world – during the last year 17,148 ships passed through the Canal – reducing emissions, saving time, and operating costs to shippers. The rapid increase in ship size from the “Post-Suezmax” (> 12,000 TEU) to the latest container vessels (> 19,000 TEU) now requires enlargements of port facilities and canals.
A project of this magnitude, and with potentially negative environmental outcomes, requires a transparent and scientifically sound “Environmental Impact Assessment” (EIA). An explicit obligation on Parties to the Convention on Biological Diversity (https://www.cbd.int/doc/ legal/cbd-en.pdf) was made to consider transboundary impacts on biodiversity, particularly those associated with invasive non-indigenous species
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