280 research outputs found
Cosmological Hints of Modified Gravity ?
The recent measurements of Cosmic Microwave Background temperature and
polarization anisotropies made by the Planck satellite have provided impressive
confirmation of the CDM cosmological model. However interesting hints
of slight deviations from CDM have been found, including a
c.l. preference for a "modified gravity" structure formation scenario. In this
paper we confirm the preference for a modified gravity scenario from Planck
2015 data, find that modified gravity solves the so-called anomaly
in the CMB angular spectrum, and constrains the amplitude of matter density
fluctuations to , in better agreement with
weak lensing constraints. Moreover, we find a lower value for the reionization
optical depth of (to be compared with the value of obtained in the standard scenario), more consistent with
recent optical and UV data. We check the stability of this result by
considering possible degeneracies with other parameters, including the neutrino
effective number, the running of the spectral index and the amount of
primordial helium. The indication for modified gravity is still present at
about c.l., and could become more significant if lower values of
were to be further confirmed by future cosmological and astrophysical data.Comment: 10 pages, 5 figures. Minor revisions, accepted for publication on PR
Reconciling Planck with the local value of in extended parameter space
The recent determination of the local value of the Hubble constant by Riess
et al, 2016 (hereafter R16) is now 3.3 sigma higher than the value derived from
the most recent CMB anisotropy data provided by the Planck satellite in a LCDM
model. Here we perform a combined analysis of the Planck and R16 results in an
extended parameter space, varying simultaneously 12 cosmological parameters
instead of the usual 6. We find that a phantom-like dark energy component, with
effective equation of state at 68 % c.l. can solve
the current tension between the Planck dataset and the R16 prior in an extended
CDM scenario. On the other hand, the neutrino effective number is
fully compatible with standard expectations. This result is confirmed when
including cosmic shear data from the CFHTLenS survey and CMB lensing
constraints from Planck. However, when BAO measurements are included we find
that some of the tension with R16 remains, as also is the case when we include
the supernova type Ia luminosity distances from the JLA catalog.Comment: 6 pages, 1 figur
Microfluidic detection and analysis by integration of thermocapillary actuation with a thin-film optical waveguide
We demonstrate a nonintrusive optical method for microfluidic detection and analysis based on evanescent wave sensing. The device consists of a planar thin-film waveguide integrated with a microfluidic chip for directed surface flow. Microliter droplets are electronically transported and positioned over the waveguide surface by thermocapillary actuation. The attenuated intensity of propagating modes is used to detect droplet location, to monitor dye concentration in aqueous solutions, and to measure reaction rates with increasing surface temperature for a chromogenic biochemical assay. This study illustrates a few of the capabilities possible by direct integration of optical sensing with surface-directed fluidic devices
Running the running
We use the recent observations of Cosmic Microwave Background temperature and
polarization anisotropies provided by the Planck satellite experiment to place
constraints on the running and the running of the running of the spectral index
of primordial scalar fluctuations. We find
and at
, suggesting the presence of a running of the running at the
level of two standard deviations. We find no significant correlation between
and foregrounds parameters, with the exception of the
point sources amplitude at , , which shifts by
half sigma when the running of the running is considered. We further study the
cosmological implications of such preference for
by including in the analysis the
lensing amplitude , the curvature parameter , and the sum of
neutrino masses . We find that when the running of the running is
considered, Planck data are more compatible with the standard expectations of
and but still hint at possible deviations. The
indication for survives at two standard deviations when
external datasets such as BAO and CFHTLenS are included in the analysis, and
persists at standard deviations when CMB lensing is considered. We
discuss the possibility of constraining with current and
future measurements of CMB spectral distortions, showing that an experiment
like PIXIE could provide strong constraints on and
.Comment: 10+1 pages, 9 figures, 10 tables. Matches published versio
Cosmological limits on neutrino unknowns versus low redshift priors
Recent Cosmic Microwave Background (CMB) temperature and polarization
anisotropy measurements from the Planck mission have significantly improved
previous constraints on the neutrino masses as well as the bounds on extended
models with massless or massive sterile neutrino states. However, due to
parameter degeneracies, additional low redshift priors are mandatory in order
to sharpen the CMB neutrino bounds. We explore here the role of different
priors on low redshift quantities, such as the Hubble constant, the cluster
mass bias, and the reionization optical depth . Concerning current priors
on the Hubble constant and the cluster mass bias, the bounds on the neutrino
parameters may differ appreciably depending on the choices adopted in the
analyses. With regard to future improvements in the priors on the reionization
optical depth, a value of , motivated by astrophysical
estimates of the reionization redshift, would lead to ~eV at
~CL, when combining the full \textit{Planck} measurements, Baryon
Acoustic Oscillation and Planck clusters data, thereby opening the window to
unravel the neutrino mass hierarchy with existing cosmological probes.Comment: 12 pages, 5 figure
Microfluidic actuation by modulation of surface stresses
We demonstrate the active manipulation of nanoliter liquid samples on the surface of a glass or silicon substrate by combining chemical surface patterning with electronically addressable microheater arrays. Hydrophilic lanes designate the possible routes for liquid migration while activation of specific heater elements determine the trajectories. The induced temperature fields spatially modulate the liquid surface tension thereby providing electronic control over the direction, timing, and flow rate of continuous streams or discrete drops. Temperature maps can be programed to move, split, trap, and mix ultrasmall volumes without mechanically moving parts and with low operating voltages of 2–3 V. This method of fluidic actuation allows direct accessibility to liquid samples for handling and diagnostic purposes and provides an attractive platform for palm-sized and battery-powered analysis and synthesis
Constraining Dark Energy Dynamics in Extended Parameter Space
Dynamical dark energy has been recently suggested as a promising and physical way to solve the 3 sigma tension on the value of the Hubble constant H0 between the direct measurement of Riess et al. (2016) (R16, hereafter) and the indirect constraint from Cosmic Microwave Anisotropies obtained by the Planck satellite under the assumption of a CDM model. In this paper, by parameterizing dark energy evolution using the w0-wa approach, and considering a 12 parameter extended scenario, we find that: a) the tension on the Hubble constant can indeed be solved with dynamical dark energy, b) a cosmological constant is ruled out at more than 95% c.l. by the Planck+R16 dataset, and c) all of the standard quintessence and half of the "downward going" dark energy model space (characterized by an equation of state that decreases with time) is also excluded at more than 95% c.l. These results are further confirmed when cosmic shear, CMB lensing, or SN Ia luminosity distance data are also included. However, tension remains with the BAO dataset. A cosmological constant and small portion of the freezing quintessence models are still in agreement with the Planck+R16+BAO dataset at between 68% and 95% c.l. Conversely, for Planck plus a phenomenological H0 prior, both thawing and freezing quintessence models prefer a Hubble constant of less than 70 km/s/Mpc. The general conclusions hold also when considering models with non-zero spatial curvature
Implementing an Early Alert Workflow Process in Higher Education to Enhance Retention and Student Engagement
This case study examines the implementation of an early alert intervention system designed to enhance retention and student course engagement at a large suburban, public two-year degree-granting college. The focus of the study was to investigate the work-flow process and labor requirements for operationalizing the in-house intervention protocol, utilizing a Success Coach model. This paper documents the intervention procedures and reports findings pertaining to faculty time commitment and participation, frequency and prevalence of raised alert flags, and labor requirements for conducting student outreach. Cost efficiency and effectiveness are discussed, as are alternative approaches for implementation, including the use of automation and commercially available early alert software solutions. Implications of findings for the operationalization of the success coach model are considered and suggestions for further investigation are discussed.
This case study investigated preservice teachers’ perceptions of their use of “backdoor praise” (BDP)—praise that is simultaneously delayed, indirect, and embedded in teacher comments—during their final internship. Three participants representing elementary, middle, and high schools, were observed to collect baseline data on their natural use of BDP. The researcher then explained BDP and conducted two more observations of each preservice teacher and their use of BDP. Twenty-eight incidents involving 21 students were recorded; 16 students maintained long-term on-task behavior ranging from three minutes to nearly 60 minutes post-BDP. The preservice teachers were interviewed after each observation, and they all reported positive student and whole-class reactions to BDP; in addition, the student teachers reported that their use of positive comments increased while their use of negative comments and reprimands decreased. These results suggest that direct instruction in BDP helped the preservice teachers to become more aware of their own praise talk
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