670 research outputs found
List Defective Colorings: Distributed Algorithms and Applications
The distributed coloring problem is at the core of the area of distributed
graph algorithms and it is a problem that has seen tremendous progress over the
last few years. Much of the remarkable recent progress on deterministic
distributed coloring algorithms is based on two main tools: a) defective
colorings in which every node of a given color can have a limited number of
neighbors of the same color and b) list coloring, a natural generalization of
the standard coloring problem that naturally appears when colorings are
computed in different stages and one has to extend a previously computed
partial coloring to a full coloring.
In this paper, we introduce \emph{list defective colorings}, which can be
seen as a generalization of these two coloring variants. Essentially, in a list
defective coloring instance, each node is given a list of colors
together with a list of defects
such that if is colored with color , it is allowed to have at
most neighbors with color .
We highlight the important role of list defective colorings by showing that
faster list defective coloring algorithms would directly lead to faster
deterministic -coloring algorithms in the LOCAL model. Further, we
extend a recent distributed list coloring algorithm by Maus and Tonoyan [DISC
'20]. Slightly simplified, we show that if for each node it holds that
then
this list defective coloring instance can be solved in a
communication-efficient way in only communication rounds. This
leads to the first deterministic -coloring algorithm in the
standard CONGEST model with a time complexity of , matching the best time complexity in the LOCAL model up to a
factor
Distributed CONGEST Approximation of Weighted Vertex Covers and Matchings
We provide CONGEST model algorithms for approximating minimum weighted vertex
cover and the maximum weighted matching. For bipartite graphs, we show that a
-approximate weighted vertex cover can be computed
deterministically in polylogarithmic time. This generalizes a corresponding
result for the unweighted vertex cover problem shown in [Faour, Kuhn; OPODIS
'20]. Moreover, we show that in general weighted graph families that are closed
under taking subgraphs and in which we can compute an independent set of weight
at least a -fraction of the total weight, one can compute a
-approximate weighted vertex cover in
polylogarithmic time in the CONGEST model. Our result in particular implies
that in graphs of arboricity , one can compute a
-approximate weighted vertex cover.
For maximum weighted matchings, we show that a -approximate
solution can be computed deterministically in polylogarithmic CONGEST rounds
(for constant ). We also provide a more efficient randomized
algorithm. Our algorithm generalizes results of [Lotker, Patt-Shamir, Pettie;
SPAA '08] and [Bar-Yehuda, Hillel, Ghaffari, Schwartzman; PODC '17] for the
unweighted case.
Finally, we show that even in the LOCAL model and in bipartite graphs of
degree , if for some constant
, then computing a -approximation for the
unweighted minimum vertex cover problem requires rounds. This generalizes aresult of [G\"o\"os, Suomela;
DISC '12], who showed that computing a -approximation in
such graphs requires rounds
A model for transcutaneous current stimulation: simulations and experiments
Complex nerve models have been developed for describing the generation of action potentials in humans. Such nerve models have primarily been used to model implantable electrical stimulation systems, where the stimulation electrodes are close to the nerve (near-field). To address if these nerve models can also be used to model transcutaneous electrical stimulation (TES) (far-field), we have developed a TES model that comprises a volume conductor and different previously published non-linear nerve models. The volume conductor models the resistive and capacitive properties of electrodes, electrode-skin interface, skin, fat, muscle, and bone. The non-linear nerve models were used to conclude from the potential field within the volume conductor on nerve activation. A comparison of simulated and experimentally measured chronaxie values (a measure for the excitability of nerves) and muscle twitch forces on human volunteers allowed us to conclude that some of the published nerve models can be used in TES models. The presented TES model provides a first step to more extensive model implementations for TES in which e.g., multi-array electrode configurations can be teste
Sexual function after sacrospinous fixation for vaginal vault prolapse: bad or mad?
Background: The main indication for sacrospinous ligament suspension is to correct either total procidentia, a posthysterectomy vaginal vault prolapse with an associated weak cardinal uterosacral ligament complex, or a posthysterectomy enterocele. This study aimed to evaluate sexual function and anatomic outcome for patients after sacrospinous ligament suspension. Methods: For this study, 52 patients who had undergone sacrospinous ligament fixation during the preceding 5years were asked to complete the Female Sexual Function Index (FSFI) questionnaire. The patients were vaginally examined using the ICS POP score, and the results were compared with their preoperative status. For statistical analysis, GraphPad for Windows, version 4.0, was used. Results: The 52 patients were examined during a follow-up period of 38months. No major intraoperative complications were noted. Recurrence of symptomatic apical descent was noted in 6% of the patients and de novo prolapse in 13.5%. Only one patient was symptomatic. Three patients experienced de novo dyspareunia, which resolved in two cases after stitch removal. Sexual function was good, rating higher than three points for each of the domains including satisfaction, lubrication, desire, orgasm, and pain. Conclusion: Sacrospinous ligament fixation still is a valuable option for the treatment of vaginal vault prolapse. Sexual function is satisfactory, with few cases of de novo dyspareuni
Inter-Node Distance Estimation from Multipath Delay Differences of Channels to Observer Nodes
We study the estimation of distance d between two wireless nodes by means of
their wideband channels to a third node, called observer. The motivating
principle is that the channel impulse responses are similar for small d and
drift apart when d increases. Following this idea we propose specific distance
estimators based on the differences of path delays of the extractable multipath
components. In particular, we derive such estimators for rich multipath
environments and various important cases: with and without clock
synchronization as well as errors on the extracted path delays (e.g. due to
limited bandwidth). The estimators readily support (and benefit from) the
presence of multiple observers. We present an error analysis and, using ray
tracing in an exemplary indoor environment, show that the estimators perform
well in realistic conditions. We describe possible localization applications of
the proposed scheme and highlight its major advantages: it requires neither
precise synchronization nor line-of-sight connection. This could make wireless
user tracking feasible in dynamic indoor settings.Comment: To appear at IEEE ICC 2019. This work has been submitted to the IEEE
for possible publication. Copyright may be transferred without notice, after
which this version may no longer be accessibl
Novel blood protein based scaffolds for cardiovascular tissue engineering
A major challenge in cardiovascular tissue engineering is the fabrication of scaffolds, which provide appropriate morphological and mechanical properties while avoiding undesirable immune reactions. In this study electrospinning was used to fabricate scaffolds out of blood proteins for cardiovascular tissue engineering. Lyophilised porcine plasma was dissolved in deionised water at a final concentration of 7.5% m/v and blended with 3.7% m/v PEO. Electrospinning resulted in homogeneous fibre morphologies with a mean fibre diameter of 151 nm, which could be adapted to create macroscopic shapes (mats, tubes). Cross-linking with glutaraldehyde vapour improved the long-term stability of protein based scaffolds in comparison to untreated scaffolds, resulting in a mass loss of 41% and 96% after 28 days of incubation in aqueous solution, respectively
Non-invasive removal of sandblasted and acid-etched titanium palatal implants, a retrospective study
BACKGROUND Short, rough-surfaced palatal implants are an established and reliable anchor for orthodontic treatment. Until recently, removal was only possible surgically using a hollow cylinder trephine. This standard method retrieves the implant combined with a larger bone volume and is therefore considered invasive and has known complications. Lately, an explantation tool which allows a sufficient force application to break the bone-implant-connection and unscrew the palatal implant was developed and, since its introduction, has been used as the method of choice in several orthodontic offices. OBJECTIVES The aim of this study was to assess the complications caused by removing rough-surfaced palatal implants simply by unscrewing them with an explantation tool in contrast to standard protocol by surgical removal with a trephine. MATERIAL AND METHODS The removal of 73 palatal implants using a customized explantation tool has been evaluated retrospectively and was compared to an existing sample of 44 conventional surgical explantations. RESULTS The new clinical procedure resulted in successful removal of 71 (97.3 per cent) palatal implants. In two cases, the new method failed but removal with the established surgical method was still possible with no further complications. The non-invasive palatal implant removal with a customized explantation tool had less medical complications compared to an existing sample of surgical explantations. CONCLUSIONS User's opinion was that the new method is more easily executed, less invasive, and also applicable without local anaesthesia. Therefore, it is considered to be beneficial for patients and the treatment approach of choice. However, further research is needed for verificatio
Vulnerability of uneven-aged forests to storm damage
Uneven-aged forests are assumed to have a high stability against storm damage but have rarely been analysed for vulnerability to storm damage due to a lack of a sufficient empirical database. Here we model storm damage in uneven-aged forest to analyse major factors that may determine the sensitivity of this type of forests to storms based on a broad database. Data are derived of public forests in the canton Neuchâtel in West Switzerland that are dominated by silver fir and Norway spruce and managed since the beginning of the 20th century following a single-tree selection system. A unique dataset of periodical (every 5-10 years) full inventories measuring the diameter of every single tree including salvage cuttings was available for the investigation. The time series reached back until 1920 and covered an area of 16 000 ha divided into 3000 divisions. The effect of a major winter storm (‘Lothar') in December 1999 on these forests was investigated using a subset of 648 divisions. The influence of the vertical stand structure on the vulnerability of storm damage was studied using logistic regression models. To facilitate the analyses, an index of closeness to a J-shaped distribution (LikeJ) based on the number of trees in different diameter classes was developed. Besides structural indices, variables representing stand characteristics, soil-related and topography-related variables were included. The results of our study show that the overall damage level of the investigated forests was rather low. The variables that entered the model for the uneven-aged stands were different to those that are normally significant for even-aged stands. While variables like stand structure, the timing of the harvesting and topographic variables entered a multivariate statistical model as significant predictors, standard predictors for storm damage in even-aged stands such as stand density, thinning intensity or species composition were not significant. We hypothesize that the uneven-aged structure of the investigated forests may be one reason for the low damage level we observed but emphasize the need for more detailed research to support this conclusio
Pythia version 7-0.0 - a proof-of-concept version
This document describes the first proof-of-concept version of the Pythia7
program.
Pythia7 is a complete re-write of the Pythia program in C++. It is mainly
intended to be a replacement for the `Lund' family of event generators, but is
also a toolkit with a structure suitable for implementing any event generator
model.
In this document, the structure of the program is presented both from the
user and the developer point of view. It is not intended to be a complete
manual, but together with the documentation provided in the distribution, it
should be sufficient to start working with the program.Comment: 39 pages, 3 figure
Porównanie maksymalnego ciśnienia zamknięcia cewki moczowej mierzone cewnikiem typu mikrotip i cewnikiem wypełnionym powietrzem – badanie randomizowane
Background: Measurements of maximum urethral closure pressure (MUCP) are a part of urodynamic investigations preceding an incontinence surgery and a part of urethral function tests. Objectives: The aim of the study was to compare maximum urethral closure pressure determined by a microtip catheter with those measured by an air-charged catheter. Material and methods: A prospective randomized study in a tertiary referral centre. 122 female patients with urodynamic stress incontinence were randomly assigned to have their urethral pressure profi les measured at rest by both microtip and air-charged catheters. Intervention and Measurements: Each patient had three measurements taken by each catheter type. Means of the measurements were compared with regard to correlation and repeatability. For statistical analysis, an approach proposed by Bland-Altman was applied to assess the agreement between the two techniques. Results: Correlation coeffi cient between MUCP by the air-charged and the microtip catheter was r=0.8507(95% CI 0.7928 – 0.8934; pCel: Pomiar maksymalnego ciśnienia zamknięcia cewki moczowej (MUCP) jest częścią badania urodynamicznego poprzedzającego operacyjne leczenie nietrzymania moczu i częścią testow czynnościowych cewki moczowej. Celem pracy było porownanie maksymalnego ciśnienia zamknięcia cewki moczowej zmierzonego przy pomocy cewnika microtip i cewnika wypełnionego powietrzem. Materiał i metoda: Przeprowadzono prospektywne, randomizowane badanie w ośrodku trzeciego stopnia referencyjności. Do badania losowo włączono 122 kobiety z nietrzymaniem moczu, u których wykonywano profi l ciśnień w cewce moczowej w spoczynku przy pomocy zarówno cewnika microtip jak i cewnika wypełnionego powietrzem. Każda pacjentka miała wykonane trzy pomiary przy pomocy obu cewników. Średnie z pomiarów porównano w odniesieniu do korelacji i powtarzalności. Do celów statystycznych użyto metody Bland-Altmana oceniającej zgodność obu technik pomiarów. Wyniki: Współczynnik korelacji pomiędzy MUCP mierzonym cewnikiem powietrznym a cewnikiem microtip wynosił r=0,8507(95% CI 0,7928–0,8934;
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