Explicit Construction of Optimal Exact Regenerating Codes for Distributed Storage

Erasure coding techniques are used to increase the reliability of distributed storage systems while minimizing storage overhead. Also of interest is minimization of the bandwidth required to repair the system following a node failure. In a recent paper, Wu et al. characterize the tradeoff between the repair bandwidth and the amount of data stored per node. They also prove the existence of regenerating codes that achieve this tradeoff. In this paper, we introduce Exact Regenerating Codes, which are regenerating codes possessing the additional property of being able to duplicate the data stored at a failed node. Such codes require low processing and communication overheads, making the system practical and easy to maintain. Explicit construction of exact regenerating codes is provided for the minimum bandwidth point on the storage-repair bandwidth tradeoff, relevant to distributed-mail-server applications. A subspace based approach is provided and shown to yield necessary and sufficient conditions on a linear code to possess the exact regeneration property as well as prove the uniqueness of our construction. Also included in the paper, is an explicit construction of regenerating codes for the minimum storage point for parameters relevant to storage in peer-to-peer systems. This construction supports a variable number of nodes and can handle multiple, simultaneous node failures. All constructions given in the paper are of low complexity, requiring low field size in particular.Comment: 7 pages, 2 figures, in the Proceedings of Allerton Conference on Communication, Control and Computing, September 200

Interference Alignment in Regenerating Codes for Distributed Storage: Necessity and Code Constructions

Regenerating codes are a class of recently developed codes for distributed storage that, like Reed-Solomon codes, permit data recovery from any arbitrary k of n nodes. However regenerating codes possess in addition, the ability to repair a failed node by connecting to any arbitrary d nodes and downloading an amount of data that is typically far less than the size of the data file. This amount of download is termed the repair bandwidth. Minimum storage regenerating (MSR) codes are a subclass of regenerating codes that require the least amount of network storage; every such code is a maximum distance separable (MDS) code. Further, when a replacement node stores data identical to that in the failed node, the repair is termed as exact. The four principal results of the paper are (a) the explicit construction of a class of MDS codes for d = n-1 >= 2k-1 termed the MISER code, that achieves the cut-set bound on the repair bandwidth for the exact-repair of systematic nodes, (b) proof of the necessity of interference alignment in exact-repair MSR codes, (c) a proof showing the impossibility of constructing linear, exact-repair MSR codes for d < 2k-3 in the absence of symbol extension, and (d) the construction, also explicit, of MSR codes for d = k+1. Interference alignment (IA) is a theme that runs throughout the paper: the MISER code is built on the principles of IA and IA is also a crucial component to the non-existence proof for d < 2k-3. To the best of our knowledge, the constructions presented in this paper are the first, explicit constructions of regenerating codes that achieve the cut-set bound.Comment: 38 pages, 12 figures, submitted to the IEEE Transactions on Information Theory;v3 - The title has been modified to better reflect the contributions of the submission. The paper is extensively revised with several carefully constructed figures and example

Comparison of Entrainment Rate in Acrylonitrile Reactors Using Plant Data and CFD Simulations

Accurate entrainment rates are important in fluidized bed reactors for several reasons, including determination of cyclone loadings and efficiencies, sizing of diplegs, and inputs to population balance models. Entrainment correlations exist in the literature and from other sources to predict entrainment rates from fluidized beds, but they can vary by orders of magnitude. In addition, many correlations do not take into account effects of internals which are present in many types of industrial reactors. A study was undertaken to better understand entrainment rates from Sohiotype acrylonitrile fluidized bed reactors containing catalyst classified as a Geldart type A powder. As part of this study, full scale CFD models were developed using the Barracuda® computational particle fluid dynamics (CPFD®) software and validated with the help of data collected from multiple plant reactors. These models compared two different sizes of industrial-scale reactors and included all major internals including cooling coils, cyclones, cyclone diplegs and gas spargers. Data on the pressure profile and actual entrainment rate to the cyclones generated by the Barracuda models were compared to the measured pressure data and derived entrainment rate in the plant reactors. The results showed good agreement. Additionally, evaluation of using the slip factor in the model to compare the particle volume fraction in the freeboard to the actual entrainment rate was done to determine if this technique could be used in the plant setting. The slip factor as calculated by Barracuda was between 1.55-1.95 which is similar to other values in the literature

The proangiogenic capacity of polymorphonuclear neutrophils delineated by microarray technique and by measurement of neovascularization in wounded skin of CD18-deficient mice

Growing evidence supports the concept that polymorphonuclear neutrophils (PMN) are critically involved in inflammation-mediated angiogenesis which is important for wound healing and repair. We employed an oligonucleotide microarray technique to gain further insight into the molecular mechanisms underlying the proangiogenic potential of human PMN. In addition to 18 known angiogenesis-relevant genes, we detected the expression of 10 novel genes, namely midkine, erb-B2, ets-1, transforming growth factor receptor-beta(2) and -beta(3), thrombospondin, tissue inhibitor of metalloproteinase 2, ephrin A2, ephrin B2 and restin in human PMN freshly isolated from the circulation. Gene expression was confi rmed by the RT-PCR technique. In vivo evidence for the role of PMN in neovascularization was provided by studying neovascularization in a skin model of wound healing using CD18-deficient mice which lack PMN infi ltration to sites of lesion. In CD18-deficient animals, neo- vascularization was found to be signifi cantly compromised when compared with wild- type control animals which showed profound neovascularization within the granulation tissue during the wound healing process. Thus, PMN infiltration seems to facilitate inflammation mediated angiogenesis which may be a consequence of the broad spectrum of proangiogenic factors expressed by these cells. Copyright (c) 2006 S. Karger AG, Basel

Cervical length measurement by transvaginal sonography in predicting preterm labour in low risk women

Background: Preterm birth is the leading cause of perinatal morbidity and mortality. Transvaginal sonographic measurement of the cervix is a reliable alternative method for the assessment of cervical length as it allows better quality and more accurate visualization of the uterine cervix. Several studies have reported that cervical assessment on transvaginal sonography may be useful in the prediction of preterm delivery. The objective of this study was to assess cervical length at 20 to 24 weeks of gestation in low risk women and correlate with the gestational age at delivery.Methods: A prospective cohort study conducted in a tertiary care Military Hospital in Pune, India. 354 asymptomatic low risk antenatal women with gestational age of 20 to 24 weeks were studied. Cervical assessment with transvaginal sonography for the measurement of cervical length was performed using a 10 MHz transvaginal probe.Results: 7 percent women delivered preterm. The incidence of short cervix in low risk women was only 0.56%. 100% women with short cervix delivered preterm and, only 6.9% patients who had cervical length more than 25 mm delivered preterm. Cervical length 25 mm has got sensitivity and NPV of 100% and a specificity of 93.46%. However, the PPV was only 8%.Conclusions: The study reported significant inverse relation between short cervix and the occurrence of preterm delivery. Our findings suggest that cervical length can be used as a screening method for preterm labour in low risk women. However strong evidences from large randomized control trials would be required to assess its cost-effectiveness.

Radiological Spectrum of von Hippel-Lindau disease – A Case Report

Von Hippel-Lindau (VHL) disease is an autosomal dominant genetic disorder resulting from inactivation of tumor suppressiongenes located at the chromosome 3p 25.5. VHL comprises of many benign and malignant tumors along affecting varioussystems of the body with variable manifestations. A wide variation in radiological spectrum is seen as per the involvement ofparticular system or organ. The imaging modalities like Ultrasonogrphy (USG), Computerized Tomography (CT) andMagnetic Resonance Imaging (MRI) play an important role in diagnosing and treating the affected individuals. These also playequally important role in the screening and follow up of such cases. We present a case of an 18 year old female, who wasdiagnosed with VHL at the age of 10 years, where imaging modalities helped her management and follow up

Sickle Cell Mice Exhibit Elevated Plasma Bilirubin and Altered Intracranial Cerebral Blood Velocities That Are Exacerbated by Hypoxia-Reoxygenation

Sickle cell disease (SCD) is a genetic disorder characterized by sickle red blood cells (RBCs). Sickle RBCs cause cerebral vasculopathies including vaso-occlusive events, leading to ischemia-reperfusion injury and hypoxic tissue environment. To date, the physiological blood flow velocities in cerebral vessels of preclinical SCD models has not been evaluated under hypoxic-reoxygenation. In our study, we used transcranial ultrasound techniques to measure abnormal blood flow velocities in the internal carotid (ICA) and middle cerebral arteries (MCA) of transgenic sickle cell mice (SS) challenged with hypoxia-reoxygenation. Our study showed that SS mice that underwent hypoxic stress exhibited lower relative mean velocities in the MCA compared to wildtype mice (AA) (0.67 ± 0.18 vs. 0.95 ± 0.15; p \u3c  0.05). Comparison of the Lindegaard ratio between normoxia and hypoxia in SS mice suggested that the MCA underwent vasodilation (0.67 ± 0.18 vs. 0.95 ± 0.15; p \u3c 0.05). Bilirubin, a potential biomarker for cerebral vasculopathies in SCD, was higher in SS than AA mice (0.56 ± 0.28 vs. 0.05 ± 0.07 mg/dL; p \u3c 0.05). Correlation analyses revealed a significant association between bilirubin levels and blood velocities of MCA (r = −0.9377, p = 0.0002) and ICA (r = 0.8203, p = 0.0068), especially in hypoxic conditions of SS mice. We propose that the reactivity of cerebral vessels in SS mice is correlated with the elevated plasma bilirubin level

Targeting vascular endothelial growth factor receptor 2 and protein kinase d1 related pathways by a multiple kinase inhibitor in angiogenesis and inflammation related processes in vitro.

Emerging evidence suggests that the vascular endothelial growth factor receptor 2 (VEGFR2) and protein kinase D1 (PKD1) signaling axis plays a critical role in normal and pathological angiogenesis and inflammation related processes. Despite all efforts, the currently available therapeutic interventions are limited. Prior studies have also proved that a multiple target inhibitor can be more efficient compared to a single target one. Therefore, development of novel inflammatory pathway-specific inhibitors would be of great value. To test this possibility, we screened our molecular library using recombinant kinase assays and identified the previously described compound VCC251801 with strong inhibitory effect on both VEGFR2 and PKD1. We further analyzed the effect of VCC251801 in the endothelium-derived EA.hy926 cell line and in different inflammatory cell types. In EA.hy926 cells, VCC251801 potently inhibited the intracellular activation and signaling of VEGFR2 and PKD1 which inhibition eventually resulted in diminished cell proliferation. In this model, our compound was also an efficient inhibitor of in vitro angiogenesis by interfering with endothelial cell migration and tube formation processes. Our results from functional assays in inflammatory cellular models such as neutrophils and mast cells suggested an anti-inflammatory effect of VCC251801. The neutrophil study showed that VCC251801 specifically blocked the immobilized immune-complex and the adhesion dependent TNF-alpha -fibrinogen stimulated neutrophil activation. Furthermore, similar results were found in mast cell degranulation assay where VCC251801 caused significant reduction of mast cell response. In summary, we described a novel function of a multiple kinase inhibitor which strongly inhibits the VEGFR2-PKD1 signaling and might be a novel inhibitor of pathological inflammatory pathways