2,742 research outputs found
Automatic Variational Inference in Stan
Variational inference is a scalable technique for approximate Bayesian
inference. Deriving variational inference algorithms requires tedious
model-specific calculations; this makes it difficult to automate. We propose an
automatic variational inference algorithm, automatic differentiation
variational inference (ADVI). The user only provides a Bayesian model and a
dataset; nothing else. We make no conjugacy assumptions and support a broad
class of models. The algorithm automatically determines an appropriate
variational family and optimizes the variational objective. We implement ADVI
in Stan (code available now), a probabilistic programming framework. We compare
ADVI to MCMC sampling across hierarchical generalized linear models,
nonconjugate matrix factorization, and a mixture model. We train the mixture
model on a quarter million images. With ADVI we can use variational inference
on any model we write in Stan
Automatic Differentiation Variational Inference
Probabilistic modeling is iterative. A scientist posits a simple model, fits
it to her data, refines it according to her analysis, and repeats. However,
fitting complex models to large data is a bottleneck in this process. Deriving
algorithms for new models can be both mathematically and computationally
challenging, which makes it difficult to efficiently cycle through the steps.
To this end, we develop automatic differentiation variational inference (ADVI).
Using our method, the scientist only provides a probabilistic model and a
dataset, nothing else. ADVI automatically derives an efficient variational
inference algorithm, freeing the scientist to refine and explore many models.
ADVI supports a broad class of models-no conjugacy assumptions are required. We
study ADVI across ten different models and apply it to a dataset with millions
of observations. ADVI is integrated into Stan, a probabilistic programming
system; it is available for immediate use
Genetic Screening of Couples with Recurrent Spontaneous Abortion
The aim of this study was to determine the chromosomal abberations and their incidence in non-consanguineous couples with a history of two or more than two spontaneous abortion. In the study, we carried out cytogenetic analysis on 434 couples. Patients detected with chromosome abnormality were evaluated according to their pedigree analysis, and also patients’ relatives were screened for the same abnormality. Peripheral blood were taken from patients, then performed with lymphocyte culture and stained by binded using Giemsa-banding method. For each individual, 20-30-cells chromosomes were counted and around 5-10 well-binded metaphase chromosomes were karyotyped for numerical and structural chromosomal aberrations. Of 434 couples investigated, 30 (6.91%) were found to have chromosomal abnormality, in one of couples partners. In 13 of couples (2.99%), one of partners was found to be balanced translocation carrier. Of these, 7 (1.61%)were found to be reciprocal carrier, while 6 (1.38%) Robertsonian-type balanced translocation carrier. Gonadal mosaicism was found in 3 couples (0.69%), pericentric 9 inversion in 8 couples (1.85 %), while 6 couples showed different chromosomal structure from each other. These chromosomal aberrations may cause of abortion due to high incidence in general population
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Taha Toros Arşivi, Dosya Adı: Ahmet Cevat Paşa-Cevat Şakir Kabaağaçl
Microwave Electrodynamics of the Antiferromagnetic Superconductor GdBa_2Cu_3O_{7-\delta}
The temperature dependence of the microwave surface impedance and
conductivity are used to study the pairing symmetry and properties of cuprate
superconductors. However, the superconducting properties can be hidden by the
effects of paramagnetism and antiferromagnetic long-range order in the
cuprates. To address this issue we have investigated the microwave
electrodynamics of GdBa_2Cu_3O_{7-\delta}, a rare-earth cuprate superconductor
which shows long-range ordered antiferromagnetism below T_N=2.2 K, the Neel
temperature of the Gd ion subsystem. We measured the temperature dependence of
the surface resistance and surface reactance of c-axis oriented epitaxial thin
films at 10.4, 14.7 and 17.9 GHz with the parallel plate resonator technique
down to 1.4 K. Both the resistance and the reactance data show an unusual
upturn at low temperature and the resistance presents a strong peak around T_N
mainly due to change in magnetic permeability.Comment: M2S-HTCS-VI Conference Paper, 2 pages, 2 eps figures, using Elsevier
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