8 research outputs found
A Duality Based 2-Approximation Algorithm for Maximum Agreement Forest
We give a 2-approximation algorithm for the Maximum Agreement Forest problem on two rooted binary trees. This NP-hard problem has been studied extensively in the past two decades, since it can be used to compute the rooted Subtree Prune-and-Regraft (rSPR) distance between two phylogenetic trees. Our algorithm is combinatorial and its running time is quadratic in the input size. To prove the approximation guarantee, we construct a feasible dual solution for a novel linear programming formulation. In addition, we show this linear program is stronger than previously known formulations, and we give a compact formulation, showing that it can be solved in polynomial tim
Split scheduling with uniform setup times
We study a scheduling problem in which jobs
may be split into parts, where the parts of a split job may be
processed simultaneously on more than one machine. Each
part of a job requires a setup time, however, on the machine
where the job part is processed. During setup, a machine
cannot process or set up any other job. We concentrate on
the basic case in which setup times are job-, machine- and
sequence-independent. Problems of this kind were encountered
when modelling practical problems in planning dis-
aster relief operations. Our main algorithmic result is a
polynomial-time algorithm for minimising total completion
time on two parallel identical machines. We argue, why the
same problem with threemachines is not an easy extension of
the two-machine case, leaving the complexity of this case as a
tantalising open problem. We give a constant-factor approximation
algorithm for the general case with any number of
machines and a polynomial-time approximation scheme for
a fixed number of machines. For the version with the objective
to minimise total weighted completion time, we prove
NP-hardness. Finally, we conclude with an overview of the
state of the art for other split scheduling problems with job-,
machine- and sequence-independent setup times
Efficacy of halopeRIdol to decrease the burden of Delirium In adult Critically ill patiEnts (EuRIDICE): study protocol for a prospective randomised multi-centre double-blind placebo-controlled clinical trial in the Netherlands
Introduction Delirium in critically ill adults is associated
with prolonged hospital stay, increased mortality and
greater cognitive and functional decline. Current practice
guideline recommendations advocate the use of nonpharmacological strategies to reduce delirium. The
routine use of scheduled haloperidol to treat delirium is
not recommended given a lack of evidence regarding its
ability to resolve delirium nor improve relevant short-term
and longer-term outcomes. This study aims to evaluate
the efficacy and safety of haloperidol for the treatment of
delirium in adult critically ill patients to reduce days spent
with coma or delirium.
Methods and analysis EuRIDICE is a prospective, multicentre, randomised, double-blind, placebo-controlled
trial. Study population consists of adult intensive care
unit (ICU) patients without acute neurological injury who
have delirium based on a positive Intensive Care Delirium
Screening Checklist (ICDSC) or Confusion Assessment
Method for the ICU (CAM-ICU) assessment. Intervention
is intravenous haloperidol 2.5mg (or matching placebo)
every 8 hours, titrated daily based on ICDSC or CAMICU positivity to a maximum of 5mg every 8 hours,
until delirium resolution or ICU discharge. Main study
endpoint is delirium and coma-free days (DCFD) up
to 14 days after randomisation. Secondary endpoints
include (1) 28-day and 1-year mortality, (2) cognitive and
functional performance at 3 and 12 months, (3) patient
and family delirium and ICU experience, (4) psychological
sequelae during and after ICU stay, (4) safety concerns
associated with haloperidol use and (5) cost-effectiveness.
Differences in DCFDs between haloperidol and placebo
group will be analysed using Poisson regression analysis.
Study recruitment started in February 2018 and continues.
Ethics and dissemination The study has been approved
by the Medical Ethics Committee of the Erasmus University
Medical Centre Rotterdam (MEC2017-511) and by the
Institutional Review Boards of the participating sites. Its
results will be disseminated via peer-reviewed publication
and conference presentations
2-Matchings, the Traveling Salesman Problem, and the Subtour LP: A Proof of the Boyd-Carr Conjecture
Scheduling over Scenarios on Two Machines
We consider scheduling problems over scenarios where the goal is to find a single assignment of the jobs to the machines which performs well over all possible scenarios. Each scenario is a subset of jobs that must be executed in that scenario and all scenarios are given explicitly. The two objectives that we consider are minimizing the maximum makespan over all scenarios and minimizing the sum of the makespans of all scenarios. For both versions, we give several approximation algorithms and lower bounds on their approximability. With this research into optimization problems over scenarios, we have opened a new and rich field of interesting problems
Some Insects of the Hudsonian Zone in New Mexico— V.
We consider scheduling problems over scenarios
where the goal is to find a single assignment of the jobs to
the machines which performs well over all scenarios in an
explicitly given set. Each scenario is a subset of jobs that
must be executed in that scenario. The two objectives that
we consider are minimizing the maximum makespan over
all scenarios and minimizing the sum of the makespans of
all scenarios. For both versions, we give several approximation
algorithms and lower bounds on their approximability.
We also consider some (easier) special cases. Combinatorial
optimization problems under scenarios in general, and
scheduling problems under scenarios in particular, have seen
only limited research attention so far. With this paper, we
make a step in this interesting research direction