24,227 research outputs found
A Study of Dual Polymer Retention Aids for the Retention on Titanium Dioxide Using the Dynamic Drainage Jar, Minidrinier, and Handsheets
Two types of dual polymer retention aid systems, a low molecular weight, high charge density, cationic polyamine with a high molecular weight, low charge density, cationic polyacrylamide, and the same polyamine with a high molecular weight, highly charged anionic polyacrylamide, were studied using the Dynamic Drainage Jar, the Minidrinier, and handsheets. Both systems gave higher retention than could be achieved using any of the retention aids alone, however, formation was a problem. Contact time and shear were shown to be important variables. All three testing methods were useful, the Dynamic Drainage Jar having an advantage due to its flexibility
Afterglows of Gamma-Ray Bursts: Short vs. Long GRBs
We compiled a large sample of Swift-era photometric data on long (Type II)
and short (Type I) GRB afterglows. We compare the luminosity and energetics of
the different samples to each other and to the afterglows of the pre-Swift era.
Here, we present the first results of these studies.Comment: Conference Proceedings, "Gamma-Ray Bursts 2007", Santa Fe, shortened
poster presentation; 4 pages, 3 figures; for full updated papers, go here to
arXiv:0712.2186 and also here to arXiv:0804.195
The ECLAIRs telescope onboard the SVOM mission for gamma-ray burst studies
The X- and gamma-ray telescope ECLAIRs onboard the future mission for
gamma-ray burst studies SVOM (Space-based multi-band astronomical Variable
Objects Monitor) is foreseen to operate in orbit from 2013 on. ECLAIRs will
provide fast and accurate GRB triggers to other onboard telescopes, as well as
to the whole GRB community, in particular ground-based follow-up telescopes.
With its very low energy threshold ECLAIRs is particularly well suited for the
detection of highly redshifted GRB. The ECLAIRs X- and gamma-ray imaging camera
(CXG), used for GRB detection and localization, is combined with a soft X-ray
telescope (SXT) for afterglow observations and position refinement. The CXG is
a 2D-coded mask imager with a 1024 cm detection plane made of 8080
CdTe pixels, sensitive from 4 to 300 keV, with imaging capabilities up to about
120 keV and a localization accuracy better than 10 arcmin. The CXG permanently
observes a 2 sr-wide field of the sky and provides photon data to the onboard
science and triggering unit (UTS) which detects GRB by count-rate increases or
by the appearance of a new source in cyclic sky images. The SXT is a mirror
focusing X-ray telescope operating from 0.3 to 2 keV with a sensitivity of 1
mCrab for 100 s observations. The spacecraft slews within 3 min in
order to place the GRB candidate into the 2323 arcmin field of view
of the SXT, after which it refines the GRB position to about 10 arcsec. GRB
alerts are transmitted to ground-observers within tens of seconds via a VHF
network and all detected photons are available hours later for detailed
analysis. In this paper we present the ECLAIRs concepts, with emphasis on the
expected performances.Comment: on behalf of the ECLAIRs collaboration. Proceedings of Gamma-Ray
Bursts 2007 conference, Santa Fe, USA, 5-9 November 2007. Published in AIP
conf. proc. 1000, 581-584 (2008
The neighbourhood physical environment and active travel in older adults : a systematic review and meta-analysis
BACKGROUND: Perceived and objectively-assessed aspects of the neighbourhood physical environment have been postulated to be key contributors to regular engagement in active travel (AT) in older adults. We systematically reviewed the literature on neighbourhood physical environmental correlates of AT in older adults and applied a novel meta-analytic approach to statistically quantify the strength of evidence for environment-AT associations. METHODS: Forty two quantitative studies that estimated associations of aspects of the neighbourhood built environment with AT in older adults (aged ≥ 65 years) and met selection criteria were reviewed and meta-analysed. Findings were analysed according to five AT outcomes (total walking for transport, within-neighbourhood walking for transport, combined walking and cycling for transport, cycling for transport, and all AT outcomes combined) and seven categories of the neighbourhood physical environment (residential density/urbanisation, walkability, street connectivity, access to/availability of services/destinations, pedestrian and cycling infrastructure, aesthetics and cleanliness/order, and safety and traffic). RESULTS: Most studies examined correlates of total walking for transport. A sufficient amount of evidence of positive associations with total walking for transport was found for residential density/urbanisation, walkability, street connectivity, overall access to destinations/services, land use mix, pedestrian-friendly features and access to several types of destinations. Littering/vandalism/decay was negatively related to total walking for transport. Limited evidence was available on correlates of cycling and combined walking and cycling for transport, while sufficient evidence emerged for a positive association of within-neighbourhood walking with pedestrian-friendly features and availability of benches/sitting facilities. Correlates of all AT combined mirrored those of walking for transport. Positive associations were also observed with food outlets, business/institutional/industrial destinations, availability of street lights, easy access to building entrance and human and motorised traffic volume. Several but inconsistent individual- and environmental-level moderators of associations were identified. CONCLUSIONS: Results support strong links between the neighbourhood physical environment and older adults’ AT. Future research should focus on the identification of types and mixes of destinations that support AT in older adults and how these interact with individual characteristics and other environmental factors. Future research should also aim to clarify dose-response relationships through multi-country investigations and data-pooling from diverse geographical regions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12966-017-0471-5) contains supplementary material, which is available to authorized users
Development and Validation of an Attitudinal-Profiling Tool for Patients With Asthma
This study was supported and funded by Mundipharma Pte Ltd. Online survey and statistical analysis were performed by Pei-Li Teh, Rachel Howard, Tsin-Li Chua and Jie Sun of Research Partnership Pte Ltd. Medical writing support was provided by Sen-Kwan Tay of Research2Trials Clinical Solutions Pte Ltd. The authors received honoraria from Mundipharma for their participation in the REALISE Asia Working Group meetings and discussions. Prof Price has Board membership with Mundipharma; and had received consultancy and speaker fees, grants and unrestricted funding support from Mundipharma; and payment for manuscript preparation and travel/accommodations/meeting expenses from Mundipharma. Profs Liam and David-Wang are members of the Asia-Pacific Advisory Board of Mundipharma. Profs Cho and David-Wang had received speaker fees from Mundipharma in the past. Dr Neira was an employee of Mundipharma Pte Ltd, Singapore. Ms Teh is an employee of Research Partnership Pte Ltd which conducted the REALISE Asia survey for Mundipharma. Prof Cho is a member of the Editorial Board of Allergy, Asthma & Immunology.Peer reviewedPublisher PD
Inter-pregnancy interval and risk of recurrent pre-eclampsia: systematic review and meta-analysis
Background: Women with a history of pre-eclampsia have a higher risk of developing pre-eclampsia in subsequentpregnancies. However, the role of the inter-pregnancy interval on this association is unclear.Objective: To explore the effect of inter-pregnancy interval on the risk of recurrent pre-eclampsia or eclampia.Search strategy: MEDLINE, EMBASE and LILACS were searched (inception to July 2015).Selection criteria: Cohort studies assessing the risk of recurrent pre-eclampsia in the immediate subsequentpregnancy according to different birth intervals.Data collection and analysis: Two reviewers independently performed screening, data extraction, methodologicaland quality assessment.Meta-analysis of adjusted odds ratios (aOR) with 95 % confidence intervals (CI) was used to measure the associationbetween various interval lengths and recurrent pre-eclampsia or eclampsia.Main results: We identified 1769 articles and finally included four studies with a total of 77,561 women. The meta-analysisof two studies showed that compared to inter-pregnancy intervals of 2?4 years, the aOR for recurrent pre-eclampsia was 1.01 [95 % CI 0.95 to 1.07, I2 0 %] with intervals of less than 2 years and 1.10 [95 % CI 1.02 to 1.19, I2 0 %] with intervals longerthan 4 years.Conclusion: Compared to inter-pregnancy intervals of 2 to 4 years, shorter intervals are not associated with an increasedrisk of recurrent pre-eclampsia but longer intervals appear to increase the risk. The results of this review should beinterpreted with caution as included studies are observational and thus subject to possible confounding factors.Keywords: Recurrence, Pre-eclampsia, Eclampsia, Inter-pregnancy interval, Birth interval, Meta-analysis, Systematic review,Birth spacing, Hypertensive disorders of pregnancyFil: Cormick, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Epidemiología y Salud Pública. Instituto de Efectividad Clínica y Sanitaria. Centro de Investigaciones en Epidemiología y Salud Pública; ArgentinaFil: Betran, Ana Pilar. World Health Organization; SuizaFil: Ciapponi, Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Epidemiología y Salud Pública. Instituto de Efectividad Clínica y Sanitaria. Centro de Investigaciones en Epidemiología y Salud Pública; ArgentinaFil: Hall, David R.. Stellenbosch University; Sudáfrica. Tygerberg Hospital; SudáfricaFil: Hofmyer, G. Justus. University of the Witwatersrand; Sudáfrica. University of Fort Hare; Sudáfrica. Walter Sisulu University; Sudáfric
Sampling design for compliance monitoring of surface water quality: A case study in a Polder area
International agreements such as the EU Water Framework Directive (WFD) ask for efficient sampling methods for monitoring natural resources. In this paper a general methodology for designing efficient, statistically sound monitoring schemes is described. An important decision is the choice between a design-based and a model-based method, implying the choice between probability (random) sampling and purposive sampling. For mapping purposes, model-based methods are more appropriate, whereas to obtain valid results for the universe as a whole, such as in testing water quality standards against legal standards, we generally prefer a design-based method. Four basic sampling patterns in space-time universe are described: static, synchronous, static-synchronous, and rotational. A case study is carried out for monitoring the quality of surface water at two farms in western Netherlands, wherein a synchronous sampling design is applied, with stratified simple random sampling in both space and time. To reduce laboratory costs the aliquots taken at the locations of a given sampling round are bulked to form a composite. To test the spatiotemporal mean N-total concentration during the summer half-year against the MAR standard with a power of 80% at a concentration 15% below the MAR standard and with a confidence of 95%, six to nine sampling rounds are needed with 50 to 75 locations per sampling round. For P-total the required number of sampling rounds differs strongly between the two farms, but is for both farms much larger than for N-total
Frame me if you must: PrEP framing and the impact on adherence to HIV Pre-exposure Prophylaxis
Abstract
Background
“PrEP whore” has been used both as a pejorative by PrEP opponents in the gay community and, reactively, by PrEP advocates as a method to reclaim the label from stigmatization and “slut-shaming.” The actual prevalence and impact of such PrEP-directed stigma on adherence have been insufficiently studied.
Methods
CCTG 595 was a randomized controlled PrEP demonstration project in 398 HIV-uninfected MSM and transwomen. Intracellular tenofovir-diphosphate (TFV-DP) levels at weeks 12 and 48 were used as a continuous measure of adherence. At study visits, participants were asked to describe how they perceived others’ reactions to them being on PrEP. These perceptions were categorized a priori as either “positively framed,” “negatively framed,” or both. We used Wilcoxon rank-sum to determine the association between positive and negative framing and TFV-DP levels at weeks 12 and 48.
Results
By week 4, 29% of participants reported perceiving positive reactions from members of their social groups, 5% negative, and 6% both. Reporting decreased over 48 weeks, but positive reactions were consistently reported more than negative. At week 12, no differences in mean TFV-DP levels were observed in participants with positively-framed reactions compared with those reporting no outcome or only negatively-framed (1338 [IQR, 1036-1609] vs. 1281 [946-1489] fmol/punch, P = 0.17). Additionally, no differences were observed in those with negative reactions vs. those without (1209 [977–1427] vs. 1303 [964–1545], P = 0.58). At week 48, mean TFV-DP levels trended toward being higher among those that report any reaction, regardless if positive (1335 [909–1665] vs. 1179 [841–1455], P = 0.09) or negative (1377 [1054–1603] vs. 1192 [838–1486], P = 0.10) than those reporting no reaction. At week 48, 46% of participants reported experiencing some form of PrEP-directed judgment, 23% reported being called “PrEP whore,” and 21% avoiding disclosing PrEP use.
Conclusion
Over 48 weeks, nearly half of participants reported some form of judgment or stigmatization as a consequence of PrEP use. However, individuals more frequently perceived positively framed reactions to being on PrEP than negative. Importantly, long-term PrEP adherence does not appear to suffer as a result of negative PrEP framing.
Disclosures
All authors: No reported disclosures
GRB-triggered searches for gravitational waves in LIGO data
The LIGO gravitational wave detectors have recently reached their design
sensitivity and finished a two-year science run. During this period one year of
data with unprecedented sensitivity has been collected. I will briefly describe
the status of the LIGO detectors and the overall quality of the most recent
science run. I also will present results of a search for inspiral waveforms in
gravitational wave data coincident with the short gamma ray burst detected on
1st February 2007, with its sky location error box overlapping a spiral arms of
M31. No gravitational wave signals were detected and a binary merger in M31 can
be excluded at the 99% confidence level.Comment: 5 pages, 3 figures, contributed talk, submitted to the proceedings of
Gamma Ray Bursts 2007, Santa Fe, New Mexico, November 5-9 200
Optical counterparts of undetermined type -ray Active Galactic Nuclei with blazar-like Spectral Energy Distributions
During its first four years of scientific observations, the Fermi Large Area
Telescope (Fermi-LAT) detected 3033 -ray sources above a 4
significance level. Although most of the extra-Galactic sources are active
galactic nuclei (AGN) of the blazar class, other families of AGNs are observed
too, while a still high fraction of detections () remains with
uncertain association or classification. According to the currently accepted
interpretation, the AGN -ray emission arises from inverse Compton (IC)
scattering of low energy photons by relativistic particles confined in a jet
that, in the case of blazars, is oriented very close to our line of sight.
Taking advantage of data from radio and X-ray wavelengths, which we expect to
be produced together with -rays, providing a much better source
localization potential, we focused our attention on a sample of -ray
Blazar Candidates of Undetermined Type (BCUs), starting a campaign of optical
spectroscopic observations. The main aims of our investigation include a census
of the AGN families that contribute to -ray emission and a study of
their redshift distribution, with the subsequent implications on the intrinsic
source power. We furthermore analyze which -ray properties can better
constrain the nature of the source, thus helping in the study of objects not
yet associated with a reliable low frequency counterpart. In this communication
we report on the instruments and techniques used to identify the optical
counterparts of -ray sources, we give an overview on the status of our
work, and we discuss the implications of a large scale study of -ray
emitting AGNs.Comment: 9 pages, 2 figures, proceedings of the 10th Serbian Conference on
Spectral Line Shapes in Astrophysics. JOAA, accepte
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