36 research outputs found
Diagnostic index: An open-source tool to classify TMJ OA condyles
Osteoarthritis (OA) of temporomandibular joints (TMJ) occurs in about 40% of the patients who present TMJ disorders. Despite its prevalence, OA diagnosis and treatment remain controversial since there are no clear symptoms of the disease, especially in early stages. Quantitative tools based on 3D imaging of the TMJ condyle have the potential to help characterize TMJ OA changes. The goals of the tools proposed in this study are to ultimately develop robust imaging markers for diagnosis and assessment of treatment efficacy. This work proposes to identify differences among asymptomatic controls and different clinical phenotypes of TMJ OA by means of Statistical Shape Modeling (SSM), obtained via clinical expert consensus. From three different grouping schemes (with 3, 5 and 7 groups), our best results reveal that that the majority (74.5%) of the classifications occur in agreement with the groups assigned by consensus between our clinical experts. Our findings suggest the existence of different disease-based phenotypic morphologies in TMJ OA. Our preliminary findings with statistical shape modeling based biomarkers may provide a quantitative staging of the disease. The methodology used in this study is included in an open source image analysis toolbox, to ensure reproducibility and appropriate distribution and dissemination of the solution proposed
Non Linear Current Response of a Many-Level Tunneling System: Higher Harmonics Generation
The fully nonlinear response of a many-level tunneling system to a strong
alternating field of high frequency is studied in terms of the
Schwinger-Keldysh nonequilibrium Green functions. The nonlinear time dependent
tunneling current is calculated exactly and its resonance structure is
elucidated. In particular, it is shown that under certain reasonable conditions
on the physical parameters, the Fourier component is sharply peaked at
, where is the spacing between
two levels. This frequency multiplication results from the highly nonlinear
process of photon absorption (or emission) by the tunneling system. It is
also conjectured that this effect (which so far is studied mainly in the
context of nonlinear optics) might be experimentally feasible.Comment: 28 pages, LaTex, 7 figures are available upon request from
[email protected], submitted to Phys.Rev.
Enhanced stability of the square lattice of a classical bilayer Wigner crystal
The stability and melting transition of a single layer and a bilayer crystal
consisting of charged particles interacting through a Coulomb or a screened
Coulomb potential is studied using the Monte-Carlo technique. A new melting
criterion is formulated which we show to be universal for bilayer as well as
for single layer crystals in the case of (screened) Coulomb, Lennard--Jones and
1/r^{12} repulsive inter-particle interactions. The melting temperature for the
five different lattice structures of the bilayer Wigner crystal is obtained,
and a phase diagram is constructed as a function of the interlayer distance. We
found the surprising result that the square lattice has a substantial larger
melting temperature as compared to the other lattice structures. This is a
consequence of the specific topology of the defects which are created with
increasing temperature and which have a larger energy as compared to the
defects in e.g. a hexagonal lattice.Comment: Accepted for publication in Physical Review
Adiabatic quantum pump in the presence of external ac voltages
We investigate a quantum pump which in addition to its dynamic pump
parameters is subject to oscillating external potentials applied to the
contacts of the sample. Of interest is the rectification of the ac currents
flowing through the mesoscopic scatterer and their interplay with the quantum
pump effect. We calculate the adiabatic dc current arising under the
simultaneous action of both the quantum pump effect and classical
rectification. In addition to two known terms we find a third novel
contribution which arises from the interference of the ac currents generated by
the external potentials and the ac currents generated by the pump. The
interference contribution renormalizes both the quantum pump effect and the ac
rectification effect. Analysis of this interference effect requires a
calculation of the Floquet scattering matrix beyond the adiabatic approximation
based on the frozen scattering matrix alone. The results permit us to find the
instantaneous current. In addition to the current generated by the oscillating
potentials, and the ac current due to the variation of the charge of the frozen
scatterer, there is a third contribution which represents the ac currents
generated by an oscillating scatterer. We argue that the resulting pump effect
can be viewed as a quantum rectification of the instantaneous ac currents
generated by the oscillating scatterer. These instantaneous currents are an
intrinsic property of a nonstationary scattering process.Comment: 11 pages, 1 figur
Anthropogenic Space Weather
Anthropogenic effects on the space environment started in the late 19th
century and reached their peak in the 1960s when high-altitude nuclear
explosions were carried out by the USA and the Soviet Union. These explosions
created artificial radiation belts near Earth that resulted in major damages to
several satellites. Another, unexpected impact of the high-altitude nuclear
tests was the electromagnetic pulse (EMP) that can have devastating effects
over a large geographic area (as large as the continental United States). Other
anthropogenic impacts on the space environment include chemical release ex-
periments, high-frequency wave heating of the ionosphere and the interaction of
VLF waves with the radiation belts. This paper reviews the fundamental physical
process behind these phenomena and discusses the observations of their impacts.Comment: 71 pages, 35 figure
Translationally invariant calculations of form factors, nucleon densities and momentum distributions for finite nuclei with short-range correlations included
Relying upon our previous treatment of the density matrices for nuclei (in
general, nonrelativistic self-bound finite systems) we are studying a combined
effect of center-of-mass motion and short-range nucleon-nucleon correlations on
the nucleon density and momentum distributions in light nuclei ( and
). Their intrinsic ground-state wave functions are constructed in the
so-called fixed center-of-mass approximation, starting with mean-field Slater
determinants modified by some correlator (e.g., after Jastrow or Villars). We
develop the formalism based upon the Cartesian or boson representation, in
which the coordinate and momentum operators are linear combinations of the
creation and annihilation operators for oscillatory quanta in the three
different space directions, and get the own "Tassie-Barker" factors for each
distribution and point out other model-independent results. After this
separation of the center-of-mass motion effects we propose additional analytic
means in order to simplify the subsequent calculations (e.g., within the
Jastrow approach or the unitary correlation operator method). The charge form
factors, densities and momentum distributions of and
evaluated by using the well known cluster expansions are compared with data,
our exact (numerical) results and microscopic calculations.Comment: 19 pages, 6 figure
Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.
BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362
Comparing Estimation Algorithms for Camera Position and Orientation
State estimation deals with estimation of the state of an object of interest by observing noisy measurements. The process to obtain the state estimations is called filtering. In this report several filters are compared to an existing one. The new filters deal with nonlinear process and measurement models in a different way than the existing filter. Instead of approximating the nonlinear transformations the probability densities are approximated by a set of points which undergo the nonlinear transformation. The application for which the filters will be used is to estimate the position and orientation of a camera in a markerless environment, using data from an inertial measurement unit and a camera. It is found that the corresponding process and measurement models contain nonlinearities and therefore an accuracy improvement is expected with the new filters. The new filters are variations of the so-called unscented Kalman filter. Also a discussion on the marginalized particle filter is presented. Instead of using randomly chosen samples as in the particle filter methods, the unscented Kalman filter uses deterministically chosen points. The marginalized particle filter partitions the variables of the system in a linear and a nonlinear part. Linear Kalman filters are applied to the linear variables and a particle filter to the nonlinear variables, thus reducing the computational load. Details of various implementations of the filters are given, as well as the motivation for the specific implementations. Tests are carried out to assess the performance of the filters. This is done with both simulation data and real measurements. A comparison is made to the original extended Kalman filter. The tests are focussed on accuracy and computational load. Results showed that the use of the new filters did not improve accuracy. This is mainly due to the fact that the nonlinearities are not so severe. Furthermore the filters had a higher computational load, which is an important aspect in the system reviewed in this report. Therefore the current filter need not to be replaced. The unscented Kalman filter is a good alternative to the EKF in case of new applications, since it can handle the system in a black-box manner in contrast to the EKF