Efficient evaluation of polynomials over finite fields

A method is described which allows to evaluate efficiently a polynomial in a (possibly trivial) extension of the finite field of its coefficients. Its complexity is shown to be lower than that of standard techniques when the degree of the polynomial is large with respect to the base field. Applications to the syndrome computation in the decoding of cyclic codes, Reed-Solomon codes in particular, are highlighted.Comment: presented at AusCTW 201

On the Decoding Complexity of Cyclic Codes Up to the BCH Bound

The standard algebraic decoding algorithm of cyclic codes $[n,k,d]$ up to the BCH bound $t$ is very efficient and practical for relatively small $n$ while it becomes unpractical for large $n$ as its computational complexity is $O(nt)$. Aim of this paper is to show how to make this algebraic decoding computationally more efficient: in the case of binary codes, for example, the complexity of the syndrome computation drops from $O(nt)$ to $O(t\sqrt n)$, and that of the error location from $O(nt)$ to at most $\max \{O(t\sqrt n), O(t^2\log(t)\log(n))\}$.Comment: accepted for publication in Proceedings ISIT 2011. IEEE copyrigh

Polynomial evaluation over finite fields: new algorithms and complexity bounds

An efficient evaluation method is described for polynomials in finite fields. Its complexity is shown to be lower than that of standard techniques, when the degree of the polynomial is large enough compared to the field characteristic. Specifically, if n is the degree of the polynomiaI, the asymptotic complexity is shown to be $${O(\sqrt{n})}$$ , versus O(n) of classical algorithms. Applications to the syndrome computation in the decoding of Reed-Solomon codes are highlighte

Polynomial evaluation over finite fields: new algorithms and complexity bounds

An efficient evaluation method is described for polynomials in finite fields. Its complexity is shown to be lower than that of standard techniques when the degree of the polynomial is large enough. Applications to the syndrome computation in the decoding of Reed-Solomon codes are highlighted.Comment: accepted for publication in Applicable Algebra in Engineering, Communication and Computing. The final publication will be available at springerlink.com. DOI: 10.1007/s00200-011-0160-

Profiling Web Archives

PDF of a powerpoint presentation from the 2014 International Internet Preservation Consortium (IIPC) General Assembly, Paris, France, May 21, 2014. Also available on Slideshare.https://digitalcommons.odu.edu/computerscience_presentations/1011/thumbnail.jp

The association between indwelling urinary catheter use in the elderly and urinary tract infection in acute care

BACKGROUND: The use of indwelling urinary catheters (IUCs) is thought to be the most significant risk factor for developing nosocomial urinary tract infections (UTIs). However, it is unclear how many elderly patients have preexisting bacteriuria prior to IUC placement. The purpose of this study was to determine 1) the frequency and appropriateness of IUC use in the Emergency Department (ED) in elderly patients admitted to our acute care hospital, 2) the percentage of elderly patients with an IUC who were discharged from the hospital with a diagnosis of UTI, 3) the percentage of patients with IUCs who were diagnosed and treated for UTI in the ED or who had admission bacteriuria ≥10(5 )organisms/ml indicating preexisting UTI, and 4) the percentage of patients with no indication of UTI on admission who had inappropriately placed IUCs and subsequently were diagnosed with a UTI. METHODS: Retrospective chart review. Chi square used to test significance of differences in proportions. RESULTS: Seventy three percent of patients who received an IUC in the ED were elderly (≥65 years old). During the study period, 277 elderly patients received an IUC prior to admission. Of these, 77 (28%) were diagnosed with UTI during their hospitalization. Fifty three (69%) of those diagnosed with a UTI by discharge either had the UTI diagnosed in the ED or had bacteriuria ≥10(5 )organisms/ml prior to IUC placement. Of the 24 elderly patients who developed a catheter-associated UTI (i.e., 9% of the elderly population who received an IUC), 11 of the IUCs were placed inappropriately. Thus, 4% of elderly patients with no indication of UTI on admission who received an inappropriate IUC in the ED had a primary or secondary diagnosis of UTI by discharge. The overall rate of nosocomial UTI due to an inappropriately placed IUC was the same in males and females. CONCLUSION: This study indicates that the strong association between IUC use and UTI may be partly explained by the high prevalence of preexisting UTI prior to IUC placement. Further prospective studies are needed to clarify the true risk vs benefit ratio for IUC use in acutely ill elderly patients

Ecosystem and Wildlife Implications of Brush: Management System Designed to Improve Water Runoff and Percolation

With the settlement of Texas and establishment of ranchers to produce cattle, there was an effort to maximize beef production. This caused serious overgrazing. In addition, there was a reduced incidence of fires across the landscape to clear out brush. These factors led to deterioration of the grazing lands and provided an opportunity for invasive intrusion by brush and other species onto the land and riparian zones. There has been a large-scale conversion from grasslands and savannahs to wildlands over the last 150 years (Scholes and Archer, 1997). The overall impacts are significantly impaired uplands and reduced percolation and surface flow of water from rainfall which caused changes and loss in basic aquatic and terrestrial habitat. The State of Texas adopted a program to study and implement brush management systems across the state to improve the water availability in streams, rivers, reservoirs and aquifers, as well as to improve the rangelands. The feasibility studies have shown great promise for improving ranchland and improving the water situation. However, there is less known about the aquatic and wildlife species response implications of brush management. Certainly, there are opportunities for improving the viability of an ecosystem through brush management strategies and continuing management practices. The purpose of this study was to evaluate the changes in hydrology and biological diversity associated with brush management in two watersheds where significant data was already available. This study focused on assessing the aquatic and terrestrial species implications related to specified brush management strategies over time. This involved an integrated analysis including modeling of the landscape, assessing biological diversity and developing economic implications for the two watersheds (Twin Buttes and Edwards regions). Thus, this study is comprised of three parts: modeling of brush management strategies temporally, assessing biological diversity (aquatic and terrestrial) and estimating economic implications. This represents a complex analysis involving variable units and multiple disciplines. Previous feasibility studies of brush removal have been targeted at maximizing water runoff. This analysis is an extension that is designed to examine the implications of brush management under a more restrictive set of brush removal criteria that were chosen based upon wildlife considerations. To achieve the integration of hydrologic modeling, range ecology, and economic implications, there were three team meetings bringing together all components to review status and set priorities for the remainder of the work. In addition, scientists in the three basic groups of specialization interacted daily along with representatives of the Corps of Engineers to assure that each decision was reflected in other parts of the analyses. The major addition of this analysis to brush management feasibility studies being conducted as part of the Texas brush management plan is the consideration of wildlife and aquatic biota and assessing changes in biological diversity likely to result from alternative brush management scenarios

Parp1 Localizes within the Dnmt1 Promoter and Protects Its Unmethylated State by Its Enzymatic Activity

Aberrant hypermethylation of CpG islands in housekeeping gene promoters and widespread genome hypomethylation are typical events occurring in cancer cells. The molecular mechanisms behind these cancer-related changes in DNA methylation patterns are not well understood. Two questions are particularly important: (i) how are CpG islands protected from methylation in normal cells, and how is this protection compromised in cancer cells, and (ii) how does the genome-wide demethylation in cancer cells occur. The latter question is especially intriguing since so far no DNA demethylase enzyme has been found.Our data show that the absence of ADP-ribose polymers (PARs), caused by ectopic over-expression of poly(ADP-ribose) glycohydrolase (PARG) in L929 mouse fibroblast cells leads to aberrant methylation of the CpG island in the promoter of the Dnmt1 gene, which in turn shuts down its transcription. The transcriptional silencing of Dnmt1 may be responsible for the widespread passive hypomethylation of genomic DNA which we detect on the example of pericentromeric repeat sequences. Chromatin immunoprecipitation results show that in normal cells the Dnmt1 promoter is occupied by poly(ADP-ribosyl)ated Parp1, suggesting that PARylated Parp1 plays a role in protecting the promoter from methylation.In conclusion, the genome methylation pattern following PARG over-expression mirrors the pattern characteristic of cancer cells, supporting our idea that the right balance between Parp/Parg activities maintains the DNA methylation patterns in normal cells. The finding that in normal cells Parp1 and ADP-ribose polymers localize on the Dnmt1 promoter raises the possibility that PARylated Parp1 marks those sequences in the genome that must remain unmethylated and protects them from methylation, thus playing a role in the epigenetic regulation of gene expression