701 research outputs found
S-PRAC: Fast Partial Packet Recovery with Network Coding in Very Noisy Wireless Channels
Well-known error detection and correction solutions in wireless
communications are slow or incur high transmission overhead. Recently, notable
solutions like PRAC and DAPRAC, implementing partial packet recovery with
network coding, could address these problems. However, they perform slowly when
there are many errors. We propose S-PRAC, a fast scheme for partial packet
recovery, particularly designed for very noisy wireless channels. S-PRAC
improves on DAPRAC. It divides each packet into segments consisting of a fixed
number of small RLNC encoded symbols and then attaches a CRC code to each
segment and one to each coded packet. Extensive simulations show that S-PRAC
can detect and correct errors quickly. It also outperforms DAPRAC significantly
when the number of errors is high
Evolutionary Clustering of Apprentices' Self- Regulated Learning Behavior in Learning Journals
Learning journals are increasingly used in vocational education to foster self-regulated learning and reflective learning practices. However, for many apprentices, documenting working experiences is a difficult task. In this article, we profile apprentices' learning behavior in an online learning journal. Based on a pedagogical framework, we propose a novel multistep clustering pipeline that integrates different learning dimensions into a combined profile. Specifically, the profiles are described in terms of effort, consistency, regularity, help-seeking behavior, and quality of the written entries. Our results on two populations of chef apprentices (183 apprentices) interacting with an online learning journal (over 121K entries) show that our pipeline captures changes in learning patterns over time and yields interpretable profiles that can be related to academic performance. The obtained profiles can be used as a basis for personalized interventions, with the ultimate goal of improving the apprentices' learning experience
Superconductivity at 2.3 K in the misfit compound (PbSe)1.16(TiSe2)2
The structural misfit compound (PbSe)1.16(TiSe2)2 is reported. It is a
superconductor with a Tc of 2.3 K. (PbSe)1.16(TiSe2)2 derives from a parent
compound, TiSe2, which shows a charge density wave transition and no
superconductivity. The crystal structure, characterized by high resolution
electron microscopy and powder x-ray diffraction, consists of two layers of
1T-TiSe2 alternating with a double layer of (100) PbSe. Transport measurements
suggest that the superconductivity is induced by charge transfer from the PbSe
layers to the TiSe2 layers.Comment: 17 pages, 4 figures. To be published in Physical Review
Gene expression predicts dormant metastatic breast cancer cell phenotype
BACKGROUND: Breast cancer can recur months to decades after an initial diagnosis and treatment. The mechanisms that control tumor cell dormancy remain poorly understood, making it difficult to predict which patients will recur and thus benefit from more rigorous screening and treatments. Unfortunately, the extreme rarity of dormant DTCs has been a major obstacle to their study.
METHODS: To overcome this challenge, we developed an efficient system to isolate and study rare dormant breast cancer cells from metastatic organs including bones, which represent a major site of metastasis. After isolation of cells from the long bones, we used single cell RNA-sequencing (scRNA-seq) to profile proliferative and dormant PyMT-Bo1 breast cancer cells. We also compared this signature to dormant versus proliferative tumor cells isolated from the lungs. Finally, we compared our dormant signature to human datasets.
RESULTS: We identified a group of genes including Cfh, Gas6, Mme and Ogn that were highly expressed in dormant breast cancer cells present in the bone and lung. Expression of these genes had no impact on dormancy in murine models, but their expression correlated with disease-free survival in primary human breast cancer tumors, suggesting that these genes have predictive value in determining which patients are likely to recur.
CONCLUSIONS: Dormant breast cancer cells exhibit a distinct gene expression signature regardless of metastatic site. Genes enriched in dormant breast cancer cells correlate with recurrence-free survival in breast cancer patients
Use of a global model to understand speciated atmospheric mercury observations at five high-elevation sites
© 2015 Author(s). Atmospheric mercury (Hg) measurements using the Tekran® analytical system from five high-elevation sites (1400-3200 m elevation), one in Asia and four in the western US, were compiled over multiple seasons and years, and these data were compared with the GEOS-Chem global model. Mercury data consisted of gaseous elemental Hg (GEM) and "reactive Hg" (RM), which is a combination of the gaseous oxidized (GOM) and particulate bound ( < 2.5 μm) (PBM) fractions as measured by the Tekran® system. We used a subset of the observations by defining a "free tropospheric" (FT) data set by screening using measured water vapor mixing ratios. The oxidation scheme used by the GEOS-Chem model was varied between the standard run with Br oxidation and an alternative run with OH-O 3 oxidation. We used this model-measurement comparison to help interpret the spatio-temporal trends in, and relationships among, the Hg species and ancillary parameters, to understand better the sources and fate of atmospheric RM. The most salient feature of the data across sites, seen more in summer relative to spring, was that RM was negatively correlated with GEM and water vapor mixing ratios (WV) and positively correlated with ozone (O 3 ), both in the standard model and the observations, indicating that RM was formed in dry upper altitude air from the photo-oxidation of GEM. During a free tropospheric transport high RM event observed sequentially at three sites from Oregon to Nevada, the slope of the RM/GEM relationship at the westernmost site was-1020 ± 209 pg ng -1 , indicating near-quantitative GEM-to-RM photochemical conversion. An improved correlation between the observations and the model was seen when the model was run with the OH-O3 oxidation scheme instead of the Br oxidation scheme. This simulation produced higher concentrations of RM and lower concentrations of GEM, especially at the desert sites in northwestern Nevada. This suggests that future work should investigate the effect of Br-and O 3 -initiated gas-phase oxidation occurring simultaneously in the atmosphere, as well as aqueous and heterogeneous reactions to understand whether there are multiple global oxidants for GEM and hence multiple forms of RM in the atmosphere. If the chemical forms of RM were known, then the collection efficiency of the analytical method could be evaluated better.Taiwan. Environmental Protection Administratio
Comparative characterization of a wild type and transmembrane domain-deleted fatty acid amide hydrolase: identification of the transmembrane domain as a site for oligomerization
Fatty acid amide hydrolase (FAAH) is an integral membrane protein responsible for the hydrolysis of a number of primary and secondary fatty acid amides, including the neuromodulatory compounds anandamide and oleamide. Analysis of FAAH's primary sequence reveals the presence of a single predicted transmembrane domain at the extreme N-terminus of the enzyme. A mutant form of the rat FAAH protein lacking this N-terminal transmembrane domain (DeltaTM-FAAH) was generated and, like wild type FAAH (WT-FAAH), was found to be tightly associated with membranes when expressed in COS-7 cells. Recombinant forms of WT- and DeltaTM-FAAH expressed and purified from Escherichia coli exhibited essentially identical enzymatic properties which were also similar to those of the native enzyme from rat liver. Analysis of the oligomerization states of WT- and DeltaTM-FAAH by chemical cross-linking, sedimentation velocity analytical ultracentrifugation, and size exclusion chromatography indicated that both enzymes were oligomeric when membrane-bound and after solubilization. However, WT-FAAH consistently behaved as a larger oligomer than DeltaTM-FAAH. Additionally, SDS-PAGE analysis of the recombinant proteins identified the presence of SDS-resistant oligomers for WT-FAAH, but not for DeltaTM-FAAH. Self-association through FAAH's transmembrane domain was further demonstrated by a FAAH transmembrane domain-GST fusion protein which formed SDS-resistant dimers and large oligomeric assemblies in solution
Early infant HIV diagnosis and entry to HIV care cascade in Thailand: an observational study
Background: Early infant diagnosis of HIV is crucial for timely initiation of antiretroviral therapy (ART) in infected children who are at high risk of mortality. Early infant diagnosis with dried blood spot testing was provided by the National AIDS Programme in Thailand from 2007. We report ART initiation and vital status in children with HIV after 7 years of rollout in Thailand. / Methods: Dried blood spot samples were collected from HIV-exposed children in hospitals in Thailand and mailed to the Faculty of Associated Medical Sciences, Chiang Mai University, where HIV DNA was assessed with real-time PCR to establish HIV infection. We linked data from children with an HIV infection to the National AIDS Programme database to ascertain ART and vital status. / Findings: Between April 5, 2007, and Oct 1, 2014, 16 046 dried blood spot samples were sent from 8859 children in 364 hospitals in Thailand. Median age at first dried blood spot test was 2·1 (IQR 1·8–2·5) months. Of 7174 (81%) children with two or more samples, 223 (3%) were HIV positive (including five unconfirmed). Of 1685 (19%) children with one sample, 70 (4%) were unconfirmed positive. Of 293 (3%) children who were HIV positive, 220 (75%) registered for HIV care and 170 (58%) initiated ART. Median age at ART initiation decreased from 14·2 months (IQR 10·2–25·6) in 2007 to 6·1 months (4·2–9·2) in 2013, and the number of children initiating ART aged younger than 1 year increased from five (33%) of 15 children initiating ART in 2007 to ten (83%) of 12 initiating ART in 2013. 15 (9%) of 170 children who initiated ART died and 16 (32%) of 50 who had no ART record died. / Interpretation: Early infant diagnosis with dried blood spot testing had high uptake in primary care settings. Further improvement of linkage to HIV care is needed to ensure timely treatment of all children with an HIV infection
Differential limit on the extremely-high-energy cosmic neutrino flux in the presence of astrophysical background from nine years of IceCube data
We report a quasi-differential upper limit on the extremely-high-energy (EHE)
neutrino flux above GeV based on an analysis of nine years of
IceCube data. The astrophysical neutrino flux measured by IceCube extends to
PeV energies, and it is a background flux when searching for an independent
signal flux at higher energies, such as the cosmogenic neutrino signal. We have
developed a new method to place robust limits on the EHE neutrino flux in the
presence of an astrophysical background, whose spectrum has yet to be
understood with high precision at PeV energies. A distinct event with a
deposited energy above GeV was found in the new two-year sample, in
addition to the one event previously found in the seven-year EHE neutrino
search. These two events represent a neutrino flux that is incompatible with
predictions for a cosmogenic neutrino flux and are considered to be an
astrophysical background in the current study. The obtained limit is the most
stringent to date in the energy range between and GeV. This result constrains neutrino models predicting a three-flavor
neutrino flux of $E_\nu^2\phi_{\nu_e+\nu_\mu+\nu_\tau}\simeq2\times 10^{-8}\
{\rm GeV}/{\rm cm}^2\ \sec\ {\rm sr}10^9\ {\rm GeV}$. A significant part
of the parameter-space for EHE neutrino production scenarios assuming a
proton-dominated composition of ultra-high-energy cosmic rays is excluded.Comment: The version accepted for publication in Physical Review
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