546 research outputs found
Semi-supervised and Active-learning Scenarios: Efficient Acoustic Model Refinement for a Low Resource Indian Language
We address the problem of efficient acoustic-model refinement (continuous
retraining) using semi-supervised and active learning for a low resource Indian
language, wherein the low resource constraints are having i) a small labeled
corpus from which to train a baseline `seed' acoustic model and ii) a large
training corpus without orthographic labeling or from which to perform a data
selection for manual labeling at low costs. The proposed semi-supervised
learning decodes the unlabeled large training corpus using the seed model and
through various protocols, selects the decoded utterances with high reliability
using confidence levels (that correlate to the WER of the decoded utterances)
and iterative bootstrapping. The proposed active learning protocol uses
confidence level based metric to select the decoded utterances from the large
unlabeled corpus for further labeling. The semi-supervised learning protocols
can offer a WER reduction, from a poorly trained seed model, by as much as 50%
of the best WER-reduction realizable from the seed model's WER, if the large
corpus were labeled and used for acoustic-model training. The active learning
protocols allow that only 60% of the entire training corpus be manually
labeled, to reach the same performance as the entire data
Alternative algorithm for the computation of Lyapunov spectra of dynamical systems
Recently a new method for the computation of Lyapunov exponents that does not require rescaling and reorthogonalization was proposed Í“Rangarajan, Habib, and Ryne, Phys. Rev. Lett. 80, 3747 Í‘1998Í’Í”. In this paper we make a detailed numerical comparison of the new method and a standard algorithm, as regards accuracy and efficiency, by applying them to some typical two-, three-, and four-dimensional systems. We find that in most cases there is reasonable agreement between the Lyapunov spectra obtained using the two algorithms. The CPU times required for computation are also comparable. However, in certain strongly chaotic cases, the new method was found to be either inefficient Í‘taking a lot of CPU time for computationÍ’ or inaccurate. Í“S1063-651XÍ‘99Í’50907-0
The interaction of vortical flows with red cells in venous valve mimics
The motion of cells orthogonal to the direction of main flow is of importance in natural and engineered systems. The lateral movement of red blood cells (RBCs) distal to sudden expansion is considered to influence the formation and progression of thrombosis in venous valves, aortic aneurysms, and blood-circulating devices and is also a determining parameter for cell separation applications in flow-focusing microfluidic devices. Although it is known that the unique geometry of venous valves alters the blood flow patterns and cell distribution in venous valve sinuses, the interactions between fluid flow and RBCs have not been elucidated. Here, using a dilute cell suspension in an in vitro microfluidic model of a venous valve, we quantified the spatial distribution of RBCs by microscopy and image analysis, and using micro-particle image velocimetry and 3D computational fluid dynamics simulations, we analyzed the complex flow patterns. The results show that the local hematocrit in the valve pockets is spatially heterogeneous and is significantly different from the feed hematocrit. Above a threshold shear rate, the inertial separation of streamlines and lift forces contribute to an uneven distribution of RBCs in the vortices, the entrapment of RBCs in the vortices, and non-monotonic wall shear stresses in the valve pockets. Our experimental and computational characterization provides insights into the complex interactions between fluid flow, RBC distribution, and wall shear rates in venous valve mimics, which is of relevance to understanding the pathophysiology of thrombosis and improving cell separation efficiency
The Ndc80 complex targets Bod1 to human mitotic kinetochores
Regulation of protein phosphatase activity by endogenous protein inhibitors is an important mechanism to control protein phosphorylation in cells. We recently identified Biorientation defective 1 (Bod1) as a small protein inhibitor of protein phosphatase 2A containing the B56 regulatory subunit (PP2A-B56). This phosphatase controls the amount of phosphorylation of several kinetochore proteins and thus the establishment of load-bearing chromosome-spindle attachments in time for accurate separation of sister chromatids in mitosis. Like PP2A-B56, Bod1 directly localizes to mitotic kinetochores and is required for correct segregation of mitotic chromosomes. In this report, we have probed the spatio-temporal regulation of Bod1 during mitotic progression. Kinetochore localization of Bod1 increases from nuclear envelope breakdown until metaphase. Phosphorylation of Bod1 at threonine 95 (T95), which increases Bod1's binding to and inhibition of PP2A-B56, peaks in prometaphase when PP2A-B56 localization to kinetochores is highest. We demonstrate here that kinetochore targeting of Bod1 depends on the outer kinetochore protein Ndc80 and not PP2A-B56. Crucially, Bod1 depletion functionally affects Ndc80 phosphorylation at the N-terminal serine 55 (S55), as well as a number of other phosphorylation sites within the outer kinetochore, including Knl1 at serine 24 and 60 (S24, S60), and threonine T943 and T1155 (T943, T1155). Therefore, Ndc80 recruits a phosphatase inhibitor to kinetochores which directly feeds forward to regulate Ndc80, and Knl1 phosphorylation, including sites that mediate the attachment of microtubules to kinetochores
Nanoscale Equilibrium Crystal Shapes
The finite size and interface effects on equilibrium crystal shape (ECS) have
been investigated for the case of a surface free energy density including step
stiffness and inverse-square step-step interactions. Explicitly including the
curvature of a crystallite leads to an extra boundary condition in the solution
of the crystal shape, yielding a family of crystal shapes, governed by a shape
parameter c. The total crystallite free energy, including interface energy, is
minimized for c=0, yielding in all cases the traditional PT shape (z x3/2).
Solutions of the crystal shape for c≠0 are presented and discussed in the
context of meta-stable states due to the energy barrier for nucleation.
Explicit scaled relationships for the ECS and meta-stable states in terms of
the measurable step parameters and the interfacial energy are presented.Comment: 35 page
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