542 research outputs found
An Improved Interactive Streaming Algorithm for the Distinct Elements Problem
The exact computation of the number of distinct elements (frequency moment
) is a fundamental problem in the study of data streaming algorithms. We
denote the length of the stream by where each symbol is drawn from a
universe of size . While it is well known that the moments can
be approximated by efficient streaming algorithms, it is easy to see that exact
computation of requires space . In previous work, Cormode
et al. therefore considered a model where the data stream is also processed by
a powerful helper, who provides an interactive proof of the result. They gave
such protocols with a polylogarithmic number of rounds of communication between
helper and verifier for all functions in NC. This number of rounds
can quickly make such
protocols impractical.
Cormode et al. also gave a protocol with rounds for the exact
computation of where the space complexity is but the total communication . They managed to give round protocols with
complexity for many other interesting problems
including , Inner product, and Range-sum, but computing exactly with
polylogarithmic space and communication and rounds remained open.
In this work, we give a streaming interactive protocol with rounds
for exact computation of using bits of space and the communication is . The update
time of the verifier per symbol received is .Comment: Submitted to ICALP 201
EPIC 219217635: A Doubly Eclipsing Quadruple System Containing an Evolved Binary
We have discovered a doubly eclipsing, bound, quadruple star system in the
field of K2 Campaign 7. EPIC 219217635 is a stellar image with that
contains an eclipsing binary (`EB') with d and a second EB with
d. We have obtained followup radial-velocity (`RV')
spectroscopy observations, adaptive optics imaging, as well as ground-based
photometric observations. From our analysis of all the observations, we derive
good estimates for a number of the system parameters. We conclude that (1) both
binaries are bound in a quadruple star system; (2) a linear trend to the RV
curve of binary A is found over a 2-year interval, corresponding to an
acceleration, cm s; (3) small
irregular variations are seen in the eclipse-timing variations (`ETVs')
detected over the same interval; (4) the orbital separation of the quadruple
system is probably in the range of 8-25 AU; and (5) the orbital planes of the
two binaries must be inclined with respect to each other by at least
25. In addition, we find that binary B is evolved, and the cooler and
currently less massive star has transferred much of its envelope to the
currently more massive star. We have also demonstrated that the system is
sufficiently bright that the eclipses can be followed using small ground-based
telescopes, and that this system may be profitably studied over the next decade
when the outer orbit of the quadruple is expected to manifest itself in the ETV
and/or RV curves.Comment: Accepted for publication in MNRA
The optimization and validation of the Biotyper MALDI-TOF MS database for the identification of Gram-positive anaerobic cocci
OBJECTIVES: Gram-positive anaerobic cocci (GPAC) account for 24-31% of the anaerobic bacteria isolated from human clinical specimens. At present GPAC are underrepresented in the Biotyper MALDI-TOF MS database. Profiles of new species have yet to be added. We present the optimization of the MALDI-TOF MS database for the identification of GPAC. METHODS: Main Spectral Profiles (MSPs) were created for 108 clinical GPAC isolates. Identity was confirmed using 16S rRNA gene sequencing. Species identification was considered to be reliable if the sequence similarity with its closest relative was ≥98.7%. The optimized database was validated using 140 clinical isolates. The 16S rRNA sequencing identity was compared with the MALDI-TOF MS result. RESULTS: MSPs were added from 17 species that were not yet represented in the MALDI-TOF MS database or were underrepresented (<5 MSPs). This resulted in an increase from 53.6% (75/140) to 82.1% (115/140) of GPAC isolates that could be identified at the species level using MALDI-TOF MS. An improved log score was obtained for 51.4% (72/140) of the strains. For strains with a sequence similarity <98.7% with their closest relative (n=5) or with an inconclusive sequence identity (n=4), no identification was obtained by MALDI-TOF MS or in the latter case an identity with one of its relatives. CONCLUSIONS: For some species the MSP of the type strain was not a part of the confined cluster of the corresponding clinical isolates. Also, not all species formed a homogeneous cluster. It emphasizes the necessity of adding sufficient MSPs of human clinical isolates
HLA Class I Binding 9mer Peptides from Influenza A Virus Induce CD4+ T Cell Responses
BACKGROUND: Identification of human leukocyte antigen class I (HLA-I) restricted cytotoxic T cell (CTL) epitopes from influenza virus is of importance for the development of new effective peptide-based vaccines. METHODOLOGY/PRINCIPAL FINDINGS: In the present work, bioinformatics was used to predict 9mer peptides derived from available influenza A viral proteins with binding affinity for at least one of the 12 HLA-I supertypes. The predicted peptides were then selected in a way that ensured maximal coverage of the available influenza A strains. One hundred and thirty one peptides were synthesized and their binding affinities for the HLA-I supertypes were measured in a biochemical assay. Influenza-specific T cell responses towards the peptides were quantified using IFNgamma ELISPOT assays with peripheral blood mononuclear cells (PBMC) from adult healthy HLA-I typed donors as responder cells. Of the 131 peptides, 21 were found to induce T cell responses in 19 donors. In the ELISPOT assay, five peptides induced responses that could be totally blocked by the pan-specific anti-HLA-I antibody W6/32, whereas 15 peptides induced responses that could be completely blocked in the presence of the pan-specific anti-HLA class II (HLA-II) antibody IVA12. Blocking of HLA-II subtype reactivity revealed that 8 and 6 peptide responses were blocked by anti-HLA-DR and -DP antibodies, respectively. Peptide reactivity of PBMC depleted of CD4(+) or CD8(+) T cells prior to the ELISPOT culture revealed that effectors are either CD4(+) (the majority of reactivities) or CD8(+) T cells, never a mixture of these subsets. Three of the peptides, recognized by CD4(+) T cells showed binding to recombinant DRA1*0101/DRB1*0401 or DRA1*0101/DRB5*0101 molecules in a recently developed biochemical assay. CONCLUSIONS/SIGNIFICANCE: HLA-I binding 9mer influenza virus-derived peptides induce in many cases CD4(+) T cell responses restricted by HLA-II molecules
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