511 research outputs found
Optimization of Planck/LFI on--board data handling
To asses stability against 1/f noise, the Low Frequency Instrument (LFI)
onboard the Planck mission will acquire data at a rate much higher than the
data rate allowed by its telemetry bandwith of 35.5 kbps. The data are
processed by an onboard pipeline, followed onground by a reversing step. This
paper illustrates the LFI scientific onboard processing to fit the allowed
datarate. This is a lossy process tuned by using a set of 5 parameters Naver,
r1, r2, q, O for each of the 44 LFI detectors. The paper quantifies the level
of distortion introduced by the onboard processing, EpsilonQ, as a function of
these parameters. It describes the method of optimizing the onboard processing
chain. The tuning procedure is based on a optimization algorithm applied to
unprocessed and uncompressed raw data provided either by simulations, prelaunch
tests or data taken from LFI operating in diagnostic mode. All the needed
optimization steps are performed by an automated tool, OCA2, which ends with
optimized parameters and produces a set of statistical indicators, among them
the compression rate Cr and EpsilonQ. For Planck/LFI the requirements are Cr =
2.4 and EpsilonQ <= 10% of the rms of the instrumental white noise. To speedup
the process an analytical model is developed that is able to extract most of
the relevant information on EpsilonQ and Cr as a function of the signal
statistics and the processing parameters. This model will be of interest for
the instrument data analysis. The method was applied during ground tests when
the instrument was operating in conditions representative of flight. Optimized
parameters were obtained and the performance has been verified, the required
data rate of 35.5 Kbps has been achieved while keeping EpsilonQ at a level of
3.8% of white noise rms well within the requirements.Comment: 51 pages, 13 fig.s, 3 tables, pdflatex, needs JINST.csl, graphicx,
txfonts, rotating; Issue 1.0 10 nov 2009; Sub. to JINST 23Jun09, Accepted
10Nov09, Pub.: 29Dec09; This is a preprint, not the final versio
Insecurity for compact surfaces of positive genus
A pair of points in a riemannian manifold is secure if the geodesics
between the points can be blocked by a finite number of point obstacles;
otherwise the pair of points is insecure. A manifold is secure if all pairs of
points in are secure. A manifold is insecure if there exists an insecure
point pair, and totally insecure if all point pairs are insecure.
Compact, flat manifolds are secure. A standing conjecture says that these are
the only secure, compact riemannian manifolds. We prove this for surfaces of
genus greater than zero. We also prove that a closed surface of genus greater
than one with any riemannian metric and a closed surface of genus one with
generic metric are totally insecure.Comment: 37 pages, 11 figure
Elliptic and hyperelliptic magnetohydrodynamic equilibria
The present study is a continuation of a previous one on "hyperelliptic"
axisymmetric equilibria started in [Tasso and Throumoulopoulos, Phys. Plasmas
5, 2378 (1998)].
Specifically, some equilibria with incompressible flow nonaligned with the
magnetic field and restricted by appropriate side conditions like "isothermal"
magnetic surfaces, "isodynamicity" or P + B^2/2 constant on magnetic surfaces
are found to be reducible to elliptic integrals. The third class recovers
recent equilibria found in [Schief, Phys. Plasmas 10, 2677 (2003)]. In contrast
to field aligned flows, all solutions found here have nonzero toroidal magnetic
field on and elliptic surfaces near the magnetic axis.Comment: 9 page
Planck-LFI radiometers tuning
"This paper is part of the Prelaunch status LFI papers published on JINST:
http://www.iop.org/EJ/journal/-page=extra.proc5/jinst"
This paper describes the Planck Low Frequency Instrument tuning activities
performed through the ground test campaigns, from Unit to Satellite Levels.
Tuning is key to achieve the best possible instrument performance and tuning
parameters strongly depend on thermal and electrical conditions. For this
reason tuning has been repeated several times during ground tests and it has
been repeated in flight before starting nominal operations. The paper discusses
the tuning philosophy, the activities and the obtained results, highlighting
developments and changes occurred during test campaigns. The paper concludes
with an overview of tuning performed during the satellite cryogenic test
campaign (Summer 2008) and of the plans for the just started in-flight
calibration.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in JINST. IOP Publishing Ltd is not responsible for
any errors or omissions in this version of the manuscript or any version
derived from it. The definitive publisher authenticated version is available
online at http://dx.doi.org/10.1088/1748-0221/4/12/T12013
Planck pre-launch status: Low Frequency Instrument calibration and expected scientific performance
We give the calibration and scientific performance parameters of the Planck
Low Frequency Instrument (LFI) measured during the ground cryogenic test
campaign. These parameters characterise the instrument response and constitute
our best pre-launch knowledge of the LFI scientific performance. The LFI shows
excellent stability and rejection of instrumental systematic effects;
measured noise performance shows that LFI is the most sensitive instrument of
its kind. The set of measured calibration parameters will be updated during
flight operations through the end of the mission.Comment: Accepted for publications in Astronomy and Astrophysics. Astronomy &
Astrophysics, 2010 (acceptance date: 12 Jan 2010
Assessment of Urban Flood Vulnerability Using theSocial-Ecological-Technological Systems Framework in Six US cities
As urban populations continue to grow through the 21âst century, more people are projected to be at risk of exposure to climate change-induced extreme events. To investigate the complexity of urban floods, this study applied an interlinked social-ecological-technological systems (SETS) vulnerability framework by developing an urban flood vulnerability index for six US cities. Indicators were selected to reflect and illustrate exposure, sensitivity, and adaptive capacity to flooding for each of the three domains of SETS. We quantified 18 indicators and normalized them by the citiesâ 500-yr floodplain area at the census block group level. Clusters of flood vulnerable areas were identified differently by each SETS domain, and some areas were vulnerable to floods in more than one domain. Results are provided to support decision-making for reducing risks to flooding, by considering social, ecological, and technological vulnerability as well as hotspots where multiple sources of vulnerability coexist. The spatially explicit urban SETS flood vulnerability framework can be transferred to other regions facing challenging urban floods and other types of environmental hazards. Mapping SETS flood vulnerability helps to reveal intersections of complex SETS interactions and inform policy-making for building more resilient cities in the face of extreme events and climate change impacts
16p11.2 Locus modulates response to satiety before the onset of obesity
Background:
The 600âkb BP4-BP5 copy number variants (CNVs) at the 16p11.2 locus have been associated with a range of neurodevelopmental conditions including autism spectrum disorders and schizophrenia. The number of genomic copies in this region is inversely correlated with body mass index (BMI): the deletion is associated with a highly penetrant form of obesity (present in 50% of carriers by the age of 7 years and in 70% of adults), and the duplication with being underweight. Mechanisms underlying this energy imbalance remain unknown.
Objective:
This study aims to investigate eating behavior, cognitive traits and their relationships with BMI in carriers of 16p11.2 CNVs.
Methods:
We assessed individuals carrying a 16p11.2 deletion or duplication and their intrafamilial controls using food-related behavior questionnaires and cognitive measures. We also compared these carriers with cohorts of individuals presenting with obesity, binge eating disorder or bulimia.
Results:
Response to satiety is gene dosage-dependent in pediatric CNV carriers. Altered satiety response is present in young deletion carriers before the onset of obesity. It remains altered in adolescent carriers and correlates with obesity. Adult deletion carriers exhibit eating behavior similar to that seen in a cohort of obesity without eating disorders such as bulimia or binge eating. None of the cognitive measures are associated with eating behavior or BMI.
Conclusions:
These findings suggest that abnormal satiety response is a strong contributor to the energy imbalance in 16p11.2 CNV carriers, and, akin to other genetic forms of obesity, altered satiety responsiveness in children precedes the increase in BMI observed later in adolescence
Transcriptional Profile Associated with Clinical Outcomes in Metastatic Hormone-Sensitive Prostate Cancer Treated with Androgen Deprivation and Docetaxel
(1) Background: Androgen deprivation therapy (ADT) and docetaxel (DX) combination is a standard therapy for metastatic hormone-sensitive prostate cancer (mHSPC) patients. (2) Methods: We investigate if tumor transcriptomic analysis predicts mHSPC evolution in a multicenter retrospective biomarker study. A customized panel of 184 genes was tested in mRNA from tumor samples by the nCounter platform in 125 mHSPC patients treated with ADT+DX. Gene expression was correlated with castration-resistant prostate cancer-free survival (CRPC-FS) and overall survival (OS). (3) Results: High expression of androgen receptor (AR) signature was independently associated with longer CRPC-FS (hazard ratio (HR) 0.6, 95% confidence interval (CI) 0.3-0.9; p = 0.015), high expression of estrogen receptor (ESR) signature with longer CRPC-FS (HR 0.6, 95% CI 0.4-0.9; p = 0.019) and OS (HR 0.5, 95% CI 0.2-0.9, p = 0.024), and lower expression of tumor suppressor genes (TSG) (RB1, PTEN and TP53) with shorter OS (HR 2, 95% CI 1-3.8; p = 0.044). ARV7 expression was independently associated with shorter CRPC-FS (HR 1.5, 95% CI 1.1-2.1, p = 0.008) and OS (HR 1.8, 95% CI 1.2-2.6, p = 0.004), high ESR2 was associated with longer OS (HR 0.5, 95% CI 0.2-1, p = 0.048) and low expression of RB1 was independently associated with shorter OS (HR 1.9, 95% CI 1.1-3.2, p = 0.014). (4) Conclusions: AR, ESR, and TSG expression signatures, as well as ARV7, RB1, and ESR2 expression, have a prognostic value in mHSPC patients treated with ADT+DX
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