2,213 research outputs found
Stochastic Comparisons of Two-Units Repairable Systems
We consider two models of two-units repairable systems: cold standby system
and warm standby system. We suppose that the lifetimes and repair times of the
units are all independent exponentially distributed random variables. Using
stochastic orders we compare the lifetimes of systems under different
assumptions on the parameters of exponential distributions. We also consider a
cold standby system where the lifetimes and repair times of its units are not
necessarily exponentially distributed
Colossal magnon-phonon coupling in multiferroic EuYMnO
We report the spectra of magnetically induced electric dipole absorption in
EuYMnO from temperature dependent far infrared
spectroscopy (10-250 cm). These spectra, which occur only in the
polarization, consist of two relatively narrow electromagnon features that
onset at K and a broad absorption band that persists to
temperatures well above K. The observed excitations account for the
step up of the static dielectric constant in the ferroelectric phase. The
electromagnon at 80 cm is observed to be strongly coupled to the nearby
lowest optical phonon which transfers more than 1/2 of its spectral weight to
the magnon. We attribute the origin of the broad background absorption to the
two magnon emission decay process of the phonon.Comment: 4 pages, 3 figure
Pontic site development for fixed dental prostheses with and without soft tissue grafting: 1-year results of a cohort study
AIM
To describe and compare the pontic site development for fixed-dental prostheses (FDPs) with and without soft tissue grafting up to one-year post insertion of FDPs.
MATERIALS AND METHODS
A convenience sample of 24 patients participating in an ongoing RCT was provided with three-unit tooth-borne FDPs. Six patients received a subepithelial connective tissue graft (SCTG) at the pontic site, whereas 18 patients were treated without any soft tissue graft (CONTROL). Digital impressions were taken prior to tooth preparation, after tooth preparation, after insertion of the final FDP, and at the 1 year of follow-up. The obtained stereolithography files (STL) were superimposed and profilometric as well as linear changes of the soft tissue profile were assessed at the pontic regions. Profilometric outcomes included changes of the ridge contour, the alveolar ridge width, and the crown height of the pontic. Further outcomes assessed included: the papilla index, the pink esthetic score (PES), probing depth (PD), bleeding on probing (BOP), and plaque control record (PCR). Descriptive and nonparametric statistics were applied for all outcome measures.
RESULTS
The median profilometric contour between tooth preparation and 1 year after the insertion of the final FDP decreased by - 0.25 mm [Q1, Q3: - 0.36, 0.14] in the CONTROL group and increased by 0.61 mm [Q1, Q3: - 0.18, 1.06] in the SCTG group (intergroup p = 0.038). The alveolar ridge width between prior to tooth preparation and the one-year follow-up amounted to - 0.12 mm [Q1, Q3: - 0.74, 0.70] (= loss) in the CONTROL group and to 2.23 mm [Q1, Q3: 0.62, 3.86] (= gain) in the SCTG group (intergroup p = 0.032). At one year, the median crown height of the pontic tended to decrease by - 1.24 mm [Q1, Q3: - 2.05, - 1.05] in the SCTG group (intragroup p = 0.094) and by - 0.22 mm [Q1, Q3: - 0.58, 0.66] in the CONTROL group (intragroup p = 0.831), with significant differences between the groups (intergroup p = 0.022). The papilla index between prior to tooth preparation and one year of follow-up improved significantly in both groups (p 0.05).
CONCLUSION
Within the limitations of the present study, soft tissue grafting tends to limit contour changes at pontic sites, thus maintaining the esthetic outcomes over time. The lack of soft tissue grafting results in stable clinical outcomes; however, it may lead to a decrease in aesthetic outcomes over time.
CLINICAL RELEVANCE
Autogenous soft tissue grafting seems to be a valid therapeutic option for the development of the pontic site to restore ridge defects prior to the delivery of fixed dental prostheses and to limit dimensional changes over time
Examining the relationship between semiquantitative methods analysing concentration-time and enhancement-time curves from dynamic-contrast enhanced magnetic resonance imaging and cerebrovascular dysfunction in small vessel disease
Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can be used to examine the distribution of an intravenous contrast agent within the brain. Computational methods have been devised to analyse the contrast uptake/washout over time as reflections of cerebrovascular dysfunction. However, there have been few direct comparisons of their relative strengths and weaknesses. In this paper, we compare five semiquantitative methods comprising the slope and area under the enhancement-time curve, the slope and area under the concentration-time curve ( SlopeCon and AUCCon ), and changes in the power spectrum over time. We studied them in cerebrospinal fluid, normal tissues, stroke lesions, and white matter hyperintensities (WMH) using DCE-MRI scans from a cohort of patients with small vessel disease (SVD) who presented mild stroke. The total SVD score was associated with AUCCon in WMH ( p0.05 ) and WMH burden ( p>0.05 ). Our results show the potential of different measures extracted from concentration-time curves extracted from the same DCE examination to demonstrate cerebrovascular dysfunction better than those extracted from enhancement-time curves
Multiwavelength Photometric and Spectropolarimetric Analysis of the FSRQ 3C 279
In this paper, we present light curves for 3C 279 over a time period of six
years; from 2008 to 2014. Our multiwavelength data comprise 1 mm to gamma-rays,
with additional optical polarimetry. Based on the behaviour of the gamma-ray
light curve with respect to other bands, we identified three different activity
periods. One of the activity periods shows anomalous behaviour with no
gamma-ray counterpart associated with optical and NIR flares. Another anomalous
activity period shows a flare in gamma-rays, 1 mm and polarization degree,
however, it does not have counterparts in the UV continuum, optical and NIR
bands. We find a significant overall correlation of the UV continuum emission,
the optical and NIR bands. This correlation suggests that the NIR to UV
continuum is co-spatial. We also find a correlation between the UV continuum
and the 1 mm data, which implies that the dominant process in producing the UV
continuum is synchrotron emission. The gamma-ray spectral index shows
statistically significant variability and an anti-correlation with the
gamma-ray luminosity. We demonstrate that the dominant gamma-ray emission
mechanism in 3C 279 changes over time. Alternatively, the location of the
gamma-ray emission zone itself may change depending on the activity state of
the central engine.Comment: 32 pages, 19 figures, Accepted for publication in MNRA
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