On the Sample Complexity of Predictive Sparse Coding

The goal of predictive sparse coding is to learn a representation of examples as sparse linear combinations of elements from a dictionary, such that a learned hypothesis linear in the new representation performs well on a predictive task. Predictive sparse coding algorithms recently have demonstrated impressive performance on a variety of supervised tasks, but their generalization properties have not been studied. We establish the first generalization error bounds for predictive sparse coding, covering two settings: 1) the overcomplete setting, where the number of features k exceeds the original dimensionality d; and 2) the high or infinite-dimensional setting, where only dimension-free bounds are useful. Both learning bounds intimately depend on stability properties of the learned sparse encoder, as measured on the training sample. Consequently, we first present a fundamental stability result for the LASSO, a result characterizing the stability of the sparse codes with respect to perturbations to the dictionary. In the overcomplete setting, we present an estimation error bound that decays as \tilde{O}(sqrt(d k/m)) with respect to d and k. In the high or infinite-dimensional setting, we show a dimension-free bound that is \tilde{O}(sqrt(k^2 s / m)) with respect to k and s, where s is an upper bound on the number of non-zeros in the sparse code for any training data point.Comment: Sparse Coding Stability Theorem from version 1 has been relaxed considerably using a new notion of coding margin. Old Sparse Coding Stability Theorem still in new version, now as Theorem 2. Presentation of all proofs simplified/improved considerably. Paper reorganized. Empirical analysis showing new coding margin is non-trivial on real dataset

Comparative study of platelet indices in cirrhosis, cirrhosis with sepsis and normal population

Background: Platelet indices are the first hematologic indices to be affected in cirrhosis. Cirrhosis patients are particularly susceptible to bacterial infections. The incidence of sepsis in cirrhosis is estimated to be at least 30-50% of hospital admissions. Sepsis also causes alterations in platelet indices. We studied and compared the platelet indices namely platelet count, mean platelet volume (MPV), platelet distribution width (PDW) and platecrit in cirrhosis, cirrhosis with sepsis and normal control population.Methods: This observational study included forty cirrhosis, forty three cirrhosis with sepsis and sixty one controls. Platelet indices were reviewed and compared between the groups and correlation of platelet indices with CTP score, MELD, platelet count and spleen size was also evaluated.Results: Platelet indices were significantly altered in cirrhosis compared to normal population. MPV and PDW were significantly higher in cirrhosis compared to control population. Platelet count and platecrit were significantly lower in cirrhosis compared to control population. CTP score and MELD showed significant positive correlation with MPV and platelet count showed significant negative correlation with PD. Sepsis in cirrhosis was associated with significant decrease in platelet count and platecrit but caused significant increase in PDW compared to cirrhosis without sepsis. Cirrhosis with sepsis group had four patients with variceal bleeding with significantly higher mean PDW(19%) and significantly lower mean platecrit (0.04) compared to nonbleeding group (p value <0.05).Conclusions: Platelet indices are useful parameters in cirrhosis. Other than platelet count, PDW and platecrit are useful indices to be monitored in cirrhosis with sepsis

Understanding the Effectiveness of Carbon Management System (CMS): An Empirical Study

Despite increasing emphasis on corporate sustainability and green IS, empirical research on the relationships between specific green IS artifacts and intended outcomes (such as various resource consumption) are relatively scant. In addition, research is silent on the firm-specific factors that could influence the benefits from such artifacts. This paper seeks to fill this research gap by examining the relationship between carbon management system (CMS) and energy consumption. The paper also explores the role of the environmental management system (EMS) and human capital development (HCD) in influencing the relationship between CMS and energy consumption. The study utilizes data from secondary sources and proprietary databases. Findings from this study empirically demonstrate the environmental value of specific green IS artifacts and the role of facilitating factors

Alignments in quasar polarizations: pseudoscalar-photon mixing in the presence of correlated magnetic fields

We investigate the effects of pseudoscalar-photon mixing on electromagnetic radiation in the presence of correlated extragalactic magnetic fields. We model the Universe as a collection of magnetic domains and study the propagation of radiation through them. This leads to correlations between Stokes parameters over large scales and consistently explains the observed large-scale alignment of quasar polarizations at different redshifts within the framework of the big bang model.Comment: 12 pages, 5 figures, version published in PR

Cellular and Subcellular Oxidative Stress Parameters Following Severe Spinal Cord Injury

The present study undertook a comprehensive assessment of the acute biochemical oxidative stress parameters in both cellular and, notably, mitochondrial isolates following severe upper lumbar contusion spinal cord injury (SCI) in adult female Sprague Dawley rats. At 24 h post-injury, spinal cord tissue homogenate and mitochondrial fractions were isolated concurrently and assessed for glutathione (GSH) content and production of nitric oxide (NO•), in addition to the presence of oxidative stress markers 3-nitrotyrosine (3-NT), protein carbonyl (PC), 4-hydroxynonenal (4-HNE) and lipid peroxidation (LPO). Moreover, we assessed production of superoxide (O2•-) and hydrogen peroxide (H2O2) in mitochondrial fractions. Quantitative biochemical analyses showed that compared to sham, SCI significantly lowered GSH content accompanied by increased NO• production in both cellular and mitochondrial fractions. SCI also resulted in increased O2•- and H2O2 levels in mitochondrial fractions. Western blot analysis further showed that reactive oxygen/nitrogen species (ROS/RNS) mediated PC and 3-NT production were significantly higher in both fractions after SCI. Conversely, neither 4-HNE levels nor LPO formation were increased at 24 h after injury in either tissue homogenate or mitochondrial fractions. These results indicate that by 24 h post-injury ROS-induced protein oxidation is more prominent compared to lipid oxidation, indicating a critical temporal distinction in secondary pathophysiology that is critical in designing therapeutic approaches to mitigate consequences of oxidative stress

Rheological Behavior of Aqueous Suspensions of Laponite: New Insights into the Ageing Phenomena

In this paper, ageing behavior of suspensions of laponite with varying salt concentration is investigated using rheological tools. It is observed that the ageing is accompanied by an increase in the complex viscosity. The succeeding creep experiments performed at various ages showed damped oscillations in the strain. The characteristic time-scale of the damped oscillations, retardation time, showed a prominent decrease with the age of the system. However, this dependence weakens with an increase in the salt concentration, which is known to change microstructure of the system from glass-like to gel-like. We postulate that a decrease in the retardation time can be represented as a decrease in the viscosity (friction) of the dissipative environment surrounding the arrested entities that opposes elastic deformation of the system. We believe that ageing in colloidal glass leads to a greater ordering that enhances relative spacing between the constituents thereby reducing the frictional resistance. However, since a gel state is inherently different in structure (fractal network) than that of a glass (disordered), ageing in the same does not induce ordering. Consequently, we observe inverse dependence of retardation time on age becoming weaker with an increase in the salt concentration. We analyze these results from a perspective of ageing dynamics of both glass state and gel state of laponite suspensions.Comment: 27 Pages, 12 figure