1,209 research outputs found
PENGARUH SALIVA BUATAN DAN BELIMBING WULUH (Averrhoa bilimbi L.) TERHADAP KEKERASAN RESIN KOMPOSIT NANO HYBRID
PENGARUH SALIVA BUATAN DAN BELIMBING WULUH (Averrhoa bilimbi L.) TERHADAP KEKERASAN RESIN KOMPOSIT NANO HYBRID Elvira N. Langen1), Jimmy F. Rumampuk1), Michael A. Leman1) 1)Program studi pendidikan dokter gigi Fakultas kedokteran UNSRAT Manado, 95115 ABSTRACT Bilimbi (Averrhoa bilimbi. L) had an acid agent which can affect the surface hardness of resin composite. The change of surface hardness of resins is caused by infiltration of water contains acid agent. This process affected to bonding of matrix and filler of composite, this is due to the degradation process of resin composite. However, there is artificial saliva that can neutralize this condition. The purpose of this study was to determine the effect of immersed bilimbi and artificial saliva on surface hardness of composite. This experimental study designed in post test only control group. The samples of resin composite had 5 mm diameters and 2 mm in thickness (n= 24). Sampels divided into four groups; three groups as interverence and the other one as a control group, samples were alternately immersed in 60, 90 and 120 minutes. Post immersion samples measured by Micro Vickers Hardness Tester. Statistical analysis was performed by one-way ANOVA and post-hoc LSD test (=0.05) showed a significant difference of surface hardness on resin composite (p<0,05). It was concluded that artificial saliva increases the surface hardness of resin immersed in bilimbi. Keywords: resin composite, artificial saliva, bilimbi, surface hardness ABSTRAK Belimbing wuluh (Averrhoa bilimbi. L) memiliki kandungan asam tinggi yang dapat mempengaruhi kekerasan dari permukaan resin komposit nano hybrid. Perubahan ini disebabkan oleh proses penyerapan air yang mengandung asam sehingga mempengaruhi ikatan matriks dan filler yang menyebabkan terjadinya degradasi. Akan tetapi, saliva buatan dapat menetralkan kondisi ini. Tujuan dari penelitian ini adalah untuk mengetahui pengaruh perendaman saliva buatan dan belimbing wuluh terhadap perubahan kekerasan resin komposit nano hybrid. Jenis penelitian yang digunakan adalah eksperimental laboratorik dengan desain post test only control group. Jumlah sampel dalam penelitian sebanyak 24 sampel dengan diameter 5 mm dan tebal 2 mm, sampel dibagi menjadi empat kelompok dengan tiga durasi waktu perendaman yang berbeda yaitu 60, 90, dan 120 menit. Setelah perendaman, sampel diukur nilai kekerasannya menggunakan Micro Vickers Hardness Tester, kemudian diuji secara statistik dengan menggunakan uji one-way ANOVA dan post-hoc uji LSD (=0,05). Hasil menunjukkan adanya pengaruh signifikan dari perendaman saliva buatan dan belimbing wuluh terhadap perubahan kekerasan resin komposit (p<0.05). Kata kunci: resin komposit, saliva buatan, belimbing wuluh, kekerasan permukaan
Measurement of the Probability Distribution of Total Transmission in Random Waveguides
Measurements have been made of the probability distribution of total
transmission of microwave radiation in waveguides filled with randomly
positioned scatterers which would have values of the dimensionless conductance
g near unity. The distributions are markedly non-Gaussian and have exponential
tails. The measured distributions are accurately described by diagrammatic and
random matrix calculations carried out for nonabsorbing samples in the limit g
>> 1 when g is expressed in terms of the variance of the distribution, which
equals the degree of long-range intensity correlation across the output face of
the sample.Comment: 5 pages, 5 post script figures, RevTe
Statistical Signatures of Photon Localization
The realization that electron localization in disordered systems (Anderson
localization) is ultimately a wave phenomenon has led to the suggestion that
photons could be similarly localized by disorder. This conjecture attracted
wide interest because the differences between photons and electrons - in their
interactions, spin statistics, and methods of injection and detection - may
open a new realm of optical and microwave phenomena, and allow a detailed study
of the Anderson localization transition undisturbed by the Coulomb interaction.
To date, claims of three-dimensional photon localization have been based on
observations of the exponential decay of the electromagnetic wave as it
propagates through the disordered medium. But these reports have come under
close scrutiny because of the possibility that the decay observed may be due to
residual absorption, and because absorption itself may suppress localization.
Here we show that the extent of photon localization can be determined by a
different approach - measurement of the relative size of fluctuations of
certain transmission quantities. The variance of relative fluctuations
accurately reflects the extent of localization, even in the presence of
absorption. Using this approach, we demonstrate photon localization in both
weakly and strongly scattering quasi-one-dimensional dielectric samples and in
periodic metallic wire meshes containing metallic scatterers, while ruling it
out in three-dimensional mixtures of aluminum spheres.Comment: 5 pages, including 4 figure
A Dynamic Programming Approach to Adaptive Fractionation
We conduct a theoretical study of various solution methods for the adaptive
fractionation problem. The two messages of this paper are: (i) dynamic
programming (DP) is a useful framework for adaptive radiation therapy,
particularly adaptive fractionation, because it allows us to assess how close
to optimal different methods are, and (ii) heuristic methods proposed in this
paper are near-optimal, and therefore, can be used to evaluate the best
possible benefit of using an adaptive fraction size.
The essence of adaptive fractionation is to increase the fraction size when
the tumor and organ-at-risk (OAR) are far apart (a "favorable" anatomy) and to
decrease the fraction size when they are close together. Given that a fixed
prescribed dose must be delivered to the tumor over the course of the
treatment, such an approach results in a lower cumulative dose to the OAR when
compared to that resulting from standard fractionation. We first establish a
benchmark by using the DP algorithm to solve the problem exactly. In this case,
we characterize the structure of an optimal policy, which provides guidance for
our choice of heuristics. We develop two intuitive, numerically near-optimal
heuristic policies, which could be used for more complex, high-dimensional
problems. Furthermore, one of the heuristics requires only a statistic of the
motion probability distribution, making it a reasonable method for use in a
realistic setting. Numerically, we find that the amount of decrease in dose to
the OAR can vary significantly (5 - 85%) depending on the amount of motion in
the anatomy, the number of fractions, and the range of fraction sizes allowed.
In general, the decrease in dose to the OAR is more pronounced when: (i) we
have a high probability of large tumor-OAR distances, (ii) we use many
fractions (as in a hyper-fractionated setting), and (iii) we allow large daily
fraction size deviations.Comment: 17 pages, 4 figures, 1 tabl
Many-body localization and thermalization in the full probability distribution function of observables
We investigate the relation between thermalization following a quantum quench
and many-body localization in quasiparticle space in terms of the long-time
full distribution function of physical observables. In particular, expanding on
our recent work [E. Canovi {\em et al.}, Phys. Rev. B {\bf 83}, 094431 (2011)],
we focus on the long-time behavior of an integrable XXZ chain subject to an
integrability-breaking perturbation. After a characterization of the breaking
of integrability and the associated localization/delocalization transition
using the level spacing statistics and the properties of the eigenstates, we
study the effect of integrability-breaking on the asymptotic state after a
quantum quench of the anisotropy parameter, looking at the behavior of the full
probability distribution of the transverse and longitudinal magnetization of a
subsystem. We compare the resulting distributions with those obtained in
equilibrium at an effective temperature set by the initial energy. We find
that, while the long time distribution functions appear to always agree {\it
qualitatively} with the equilibrium ones, {\it quantitative} agreement is
obtained only when integrability is fully broken and the relevant eigenstates
are diffusive in quasi-particle space.Comment: 18 pages, 11 figure
Voxel-based 18F-FET PET segmentation and automatic clustering of tumor voxels: A significant association with IDH1 mutation status and survival in patients with gliomas.
Aim was to develop a full automatic clustering approach of the time-activity curves (TAC) from dynamic 18F-FET PET and evaluate its association with IDH1 mutation status and survival in patients with gliomas.
Thirty-seven patients (mean age: 45±13 y) with newly diagnosed gliomas and dynamic 18F-FET PET before any histopathologic investigation or treatment were retrospectively included. Each dynamic 18F-FET PET was realigned to the first image and spatially normalized in the Montreal Neurological Institute template. A tumor mask was semi-automatically generated from Z-score maps. Each brain tumor voxel was clustered in one of the 3 following centroids using dynamic time warping and k-means clustering (centroid #1: slowly increasing slope; centroid #2: rapidly increasing followed by slowly decreasing slope; and centroid #3: rapidly increasing followed by rapidly decreasing slope). The percentage of each dynamic 18F-FET TAC within tumors and other conventional 18F-FET PET parameters (maximum and mean tumor-to-brain ratios [TBRmax and TBRmean], time-to-peak [TTP] and slope) was compared between wild-type and IDH1 mutant tumors. Their prognostic value was assessed in terms of progression free-survival (PFS) and overall survival (OS) by Kaplan-Meier estimates.
Twenty patients were IDH1 wild-type and 17 IDH1 mutant. Higher percentage of centroid #1 and centroid #3 within tumors were positively (P = 0.016) and negatively (P = 0.01) correlated with IDH1 mutated status. Also, TBRmax, TBRmean, TTP, and slope discriminated significantly between tumors with and without IDH1 mutation (P range 0.01 to 0.04). Progression occurred in 22 patients (59%) at a median of 13.1 months (7.6-37.6 months) and 13 patients (35%) died from tumor progression. Patients with a percentage of centroid #1 > 90% had a longer survival compared with those with a percentage of centroid #1 < 90% (P = 0.003 for PFS and P = 0.028 for OS). This remained significant after stratification on IDH1 mutation status (P = 0.029 for PFS and P = 0.034 for OS). Compared to other conventional 18F-FET PET parameters, TTP and slope were associated with PFS and OS (P range 0.009 to 0.04).
Based on dynamic 18F-FET PET acquisition, we developed a full automatic clustering approach of TAC which appears to be a valuable noninvasive diagnostic and prognostic marker in patients with gliomas
GPU-based ultra-fast direct aperture optimization for online adaptive radiation therapy
Online adaptive radiation therapy (ART) has great promise to significantly
reduce normal tissue toxicity and/or improve tumor control through real-time
treatment adaptations based on the current patient anatomy. However, the major
technical obstacle for clinical realization of online ART, namely the inability
to achieve real-time efficiency in treatment re-planning, has yet to be solved.
To overcome this challenge, this paper presents our work on the implementation
of an intensity modulated radiation therapy (IMRT) direct aperture optimization
(DAO) algorithm on graphics processing unit (GPU) based on our previous work on
CPU. We formulate the DAO problem as a large-scale convex programming problem,
and use an exact method called column generation approach to deal with its
extremely large dimensionality on GPU. Five 9-field prostate and five 5-field
head-and-neck IMRT clinical cases with 5\times5 mm2 beamlet size and
2.5\times2.5\times2.5 mm3 voxel size were used to evaluate our algorithm on
GPU. It takes only 0.7~2.5 seconds for our implementation to generate optimal
treatment plans using 50 MLC apertures on an NVIDIA Tesla C1060 GPU card. Our
work has therefore solved a major problem in developing ultra-fast
(re-)planning technologies for online ART
Intensity distribution for waves in disordered media: deviations from Rayleigh statistics
We study the intensity distribution function, P(I), for monochromatic waves
propagating in quasi one-dimensional disordered medium, assuming that a point
source and a point detector are embedded in the bulk of the medium. We find
deviations from the Rayleigh statistics at moderately large I and a
logarithmically-normal asymptotic behavior of P(I). When the radiation source
and the detector are located close to the opposite edges of the sample (on a
distance much less then the sample length), an intermediate regime with a
stretched-exponential behavior of P(I) emerges.Comment: 4 pages Revtex, 3 figures included as eps file
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