311 research outputs found
Prospective five-year subsidence analysis of a cementless fully hydroxyapatite-coated femoral hip arthroplasty component
Early subsidence >1.5 mm is considered to be a predictive factor for later aseptic loosening of the femoral component following total hip arthroplasty (THA). The aim of this study was to assess five-year subsidence rates of the cementless hydroxyapatite-coated twinSys stem (Mathys Ltd., Bettlach, Switzerland).This prospective single-surgeon series examined consecutive patients receiving a twinSys stem at Maria Middelares Hospital, Belgium. Patients aged >85 years or unable to come to follow-up were excluded. Subsidence was assessed using Ein Bild Roentgen Analyse--Femoral Component Analysis (EBRA-FCA). Additional clinical and radiographic assessments were performed. Follow-ups were prospectively scheduled at two, five, 12, 24, and 60 months.In total, 218 THA (211 patients) were included. At five years, mean subsidence was 0.66 mm (95% CI: 0.43-0.90). Of the 211 patients, 95.2% had an excellent or good Harris Hip Score. There were few radiological changes. Kaplan-Meier analysis indicated five-year stem survival to be 98.4% (95% CI: 97.6-100%).Subsidence levels of the twinSys femoral stem throughout the five years of follow-up were substantially lower than the 1.5 mm level predictive of aseptic loosening. This was reflected in the high five-year survival rate
The quantum double well anharmonic oscillator in an external field
The aim of this paper is twofold. First of all, we study the behaviour of the
lowest eigenvalues of the quantum anharmonic oscillator under influence of an
external field. We try to understand this behaviour using perturbation theory
and compare the results with numerical calculations. This brings us to the
second aim of selecting the best method to carry out the numerical calculations
accurately.Comment: 9 pages, 6 figure
A two-parameter random walk with approximate exponential probability distribution
We study a non-Markovian random walk in dimension 1. It depends on two
parameters eps_r and eps_l, the probabilities to go straight on when walking to
the right, respectively to the left. The position x of the walk after n steps
and the number of reversals of direction k are used to estimate eps_r and
eps_l. We calculate the joint probability distribution p_n(x,k) in closed form
and show that, approximately, it belongs to the exponential family.Comment: 12 pages, updated reference to companion paper cond-mat/060126
Superstatistical fluctuations in time series: Applications to share-price dynamics and turbulence
We report a general technique to study a given experimental time series with
superstatistics. Crucial for the applicability of the superstatistics concept
is the existence of a parameter that fluctuates on a large time scale
as compared to the other time scales of the complex system under consideration.
The proposed method extracts the main superstatistical parameters out of a
given data set and examines the validity of the superstatistical model
assumptions. We test the method thoroughly with surrogate data sets. Then the
applicability of the superstatistical approach is illustrated using real
experimental data. We study two examples, velocity time series measured in
turbulent Taylor-Couette flows and time series of log returns of the closing
prices of some stock market indices
A comparative study of ethylene emanation upon nitrogen deficiency in natural accessions of Arabidopsis thaliana
An original approach to develop sustainable agriculture with less nitrogen fertilizer inputs is to tackle the cross-talk between nitrogen nutrition and plant growth regulators. In particular the gaseous hormone, ethylene, is a prime target for that purpose. The variation of ethylene production in natural accessions of the model species Arabidopsis thaliana was explored in response to the nitrate supply. Ethylene was measured with a laser-based photoacoustic detector. First, experimental conditions were established with Columbia-0 (Col-0) accession, which was grown in vitro on horizontal plates across a range of five nitrate concentrations (0.5, 1, 2.5, 5, or 10 mM). The concentrations of 1 and 10 mM nitrate were retained for further characterization. Along with a decrease of total dry biomass and higher biomass allocation to the roots, the ethylene production was 50% more important at 1 mM than at 10 mM nitrate. The total transcript levels of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASES (ACS) in roots and those of ACC OXIDASES (ACO) in shoots increased by 100% between the same treatments. This was mainly due to higher transcript levels of ACS6 and of ACO2 and ACO4 respectively. The assumption was that during nitrogen deficiency, the greater biomass allocation in favor of the roots was controlled by ethylene being released in the shoots after conversion of ACC originating from the roots. Second, biomass and ethylene productions were measured in 20 additional accessions. Across all accessions, the total dry biomass and ethylene production were correlated negatively at 1 mM but positively at 10 mM nitrate. Furthermore, polymorphism was surveyed in ACC and ethylene biosynthesis genes and gene products among accessions. Very few substitutions modifying the amino acids properties in conserved motifs of the enzymes were found in the accessions. Natural variation of ethylene production could be further explored to improve Nitrogen Use Efficiency (NUE), in particular by manipulating features like the biomass production and the timing of senescence upon nitrogen limitation
A propos d'immersion linguistique dans l'enseignement fondamental : un Ă©tat de la question
Can re-entrance be observed in force induced transitions?
A large conformational change in the reaction co-ordinate and the role of the
solvent in the formation of base-pairing are combined to settle a long standing
issue {\it i.e.} prediction of re-entrance in the force induced transition of
DNA. A direct way to observe the re-entrance, i.e a strand goes to the closed
state from the open state and again to the open state with temperature, appears
difficult to be achieved in the laboratory. An experimental protocol (in direct
way) in the constant force ensemble is being proposed for the first time that
will enable the observation of the re-entrance behavior in the
force-temperature plane. Our exact results for small oligonucleotide that forms
a hairpin structure provide the evidence that re-entrance can be observed.Comment: 12 pages and 5 figures (RevTex4). Accepted in Europhys Lett. (2009
Testing M2T/T2M Transformations
Presentado en: 16th International Conference on Model Driven Engineering Languages and Systems (MODELS 2013). Del 29 de septiembre al 4 de octubre. Miami, EEUU.Testing model-to-model (M2M) transformations is becoming a prominent topic in the current Model-driven Engineering landscape. Current approaches for transformation testing, however, assume having explicit model representations for the input domain and for the output domain of the transformation. This excludes other important transformation kinds, such as model-to-text (M2T) and text-to-model (T2M) transformations, from being properly tested since adequate model representations are missing either for the input domain or for the output domain. The contribution of this paper to overcome this gap is extending Tracts, a M2M transformation testing approach, for M2T/T2M transformation testing. The main mechanism we employ for reusing Tracts is to represent text within a generic metamodel. By this, we transform the M2T/T2M transformation specification problems into equivalent M2M transformation specification problems. We demonstrate the applicability of the approach by two examples and present how the approach is implemented for the Eclipse Modeling Framework (EMF). Finally, we apply the approach to evaluate code generation capabilities of several existing UML tools.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech. Proyecto TIN2011-2379
Quasi-exactly solvable cases of the N-dimensional symmetric quartic anharmonic oscillator
The O(N) invariant quartic anharmonic oscillator is shown to be exactly
solvable if the interaction parameter satisfies special conditions. The problem
is directly related to that of a quantum double well anharmonic oscillator in
an external field. A finite dimensional matrix equation for the problem is
constructed explicitly, along with analytical expressions for some excited
states in the system. The corresponding Niven equations for determining the
polynomial solutions for the problem are given.Comment: 7 pages, RevTeX4. A discussion on the N=1 case has been added with
the boundary condition properly treate
A generalized quantum microcanonical ensemble
We discuss a generalized quantum microcanonical ensemble. It describes
isolated systems that are not necessarily in an eigenstate of the Hamilton
operator. Statistical averages are obtained by a combination of a time average
and a maximum entropy argument to resolve the lack of knowledge about initial
conditions. As a result, statistical averages of linear observables coincide
with values obtained in the canonical ensemble. Non-canonical averages can be
obtained by taking into account conserved quantities which are non-linear
functions of the microstate.Comment: improved version, new titl
- …