2,642 research outputs found
A miniature sensor for electrical field measurements in dusty planetary atmospheres
"Dusty phenomena such as regular wind-blown dust, dust storms, and dust devils are the most important, currently active, geological processes on Mars. Electric fields larger than 100 kV/m have been measured in terrestrial dusty phenomena. Theoretical calculations predict that, close to the surface, the bulk electric fields in martian dusty phenomena reach the breakdown value of the isolating properties of thin martian air of about a few 10 kV/m. The fact that martian dusty phenomena are electrically active has important implications for dust lifting and atmospheric chemistry. Electric field sensors are usually grounded and distort the electric fields in their vicinity. Grounded sensors also produce large errors when subject to ion currents or impacts from clouds of charged particles. Moreover, they are incapable of providing information about the direction of the electric field, an important quantity. Finally, typical sensors with more than 10 cm of diameter are not capable of measuring electric fields at distances as small as a few cm from the surface. Measurements this close to the surface are necessary for studies of the effects of electric fields on dust lifting. To overcome these shortcomings, we developed the miniature electric-field sensor described in this article."http://deepblue.lib.umich.edu/bitstream/2027.42/64202/1/jpconf8_142_012075.pd
Electrostatics in wind-blown sand
Wind-blown sand, or "saltation," is an important geological process, and the
primary source of atmospheric dust aerosols. Significant discrepancies exist
between classical saltation theory and measurements. We show here that these
discrepancies can be resolved by the inclusion of sand electrification in a
physically based saltation model. Indeed, we find that electric forces enhance
the concentration of saltating particles and cause them to travel closer to the
surface, in agreement with measurements. Our results thus indicate that sand
electrification plays an important role in saltation.Comment: 4 journal pages, 5 figures, and supplementary material. Article is in
press at PR
The level of Marzano higher-order thinking skills among polytechnic students
This study aims to identify polytechnic students' level of Marzano Higher-Order Thinking Skills (HOTS) based on
two dimensions, 'Extension and Refinement of Knowledge' and 'Meaningful Use of Knowledge,' and to analyze the
difference in the students' level of Marzano HOTS based on these two dimensions depending on the students'
demographic factors. This study design was a survey using quantitative methods. A total of 313 students were
randomly selected as the survey sample. A questionnaire in the form of closed-ended questions was used as the
research instrument. Data were analyzed using frequency percentage and MANOVA test. The findings showed no
significant differences in the eight HOTS in the dimension of 'Extension and Refinement of Knowledge' with the
gender and socio-economic status (SES) factors. However, there were significant differences in the eight HOTS
with the academic achievement factor. Meanwhile, based on the dimension of 'Meaningful Use of Knowledge,' the
findings showed no significant differences in the five HOTS in this dimension with the gender and academic
achievement factors. The paper includes implications of the Higher-Order Thinking Skills (HOTS) for students to
improve their academic performance. In future research, the authors can further identify university students' HOTS
levels in the technical area
Extended polarized semiclassical model for quantum-dot cavity QED and its application to single-photon sources
We present a simple extension of the semi-classical model for a two-level
system in a cavity, in order to incorporate multiple polarized transitions,
such as those appearing in neutral and charged quantum dots (QDs), and two
nondegenerate linearly polarized cavity modes. We verify the model by exact
quantum master equation calculations, and experimentally using a neutral QD in
a polarization non-degenerate micro-cavity, in both cases we observe excellent
agreement. Finally, the usefulness of this approach is demonstrated by
optimizing a single-photon source based on polarization postselection, where we
find an increase in the brightness for optimal polarization conditions as
predicted by the model.Comment: 8 pages, for simple code see https://doi.org/10.5281/zenodo.347666
Decision aids to improve informed decision-making in pregnancy care: a systematic review
Rapid development in health care has resulted in an increasing number of screening and treatment options. Consequently, there is an urgency to provide people with relevant information about benefits and risks of healthcare options in an unbiased way. Decision aids help people to make decisions by providing unbiased non-directive research evidence about all treatment options. To determine the effectiveness of decision aids to improve informed decision making in pregnancy care. We searched MEDLINE (1953-2011), EMBASE (1980-2011), CENTRAL (CENTRAL, the Cochrane Library; 2011, Issue 4), Psycinfo (1806-2011) and Research Registers of ongoing trials (www.clinicaltrials.gov, www.controlled-trials.com). We included randomised controlled trials comparing decision aids in addition to standard care. The study population needed to be pregnant women making actual decisions concerning their pregnancy. Two independent researchers extracted data on quality of the randomised controlled trial (GRADE criteria), quality of the decision aid (IPDAS criteria), and outcome measures. Data analysis was undertaken by assessing group differences at first follow up after the interventions. Ten randomised controlled trials could be included. Pooled analyses showed that decision aids significantly increased knowledge, (weighted mean difference 11.06, 95% confidence interval 4.85-17.27), decreased decisional conflict scores (weighted mean difference -3.66, 95% confidence interval -6.65 to -0.68) and decreased anxiety (weighted mean difference -1.56, 95% confidence interval -2.75 to -0.43). Our systematic review showed the positive effect of decision aids on informed decision making in pregnancy care. Future studies should focus on increasing the uptake of decision aids in clinical practice by identifying barriers and facilitators to implementatio
GRAVITY: the Calibration Unit
We present in this paper the design and characterisation of a new sub-system
of the VLTI 2nd generation instrument GRAVITY: the Calibration Unit. The
Calibration Unit provides all functions to test and calibrate the beam combiner
instrument: it creates two artificial stars on four beams, and dispose of four
delay lines with an internal metrology. It also includes artificial stars for
the tip-tilt and pupil guiding systems, as well as four metrology pick-up
diodes, for tests and calibration of the corresponding sub-systems. The
calibration unit also hosts the reference targets to align GRAVITY to the VLTI,
and the safety shutters to avoid the metrology light to propagate in the
VLTI-lab. We present the results of the characterisation and validtion of these
differrent sub-units.Comment: 12 pages, 11 figures. Proceeding of SPIE 9146 "Optical and Infrared
Interferometry IV
Crispr/Cas9 editing reveals novel mechanisms of clustered microRNA regulation and function
MicroRNAs (miRNAs) are important regulators of diverse physiological and pathophysiological processes. MiRNA families and clusters are two key features in miRNA biology. Here we explore the use of CRISPR/Cas9 as a powerful tool to delineate the function and regulation of miRNA families and clusters. We focused on four miRNA clusters composed of miRNA members of the same family, homoclusters or different families, hetero-clusters. Our results highlight different regulatory mechanisms in miRNA cluster expression. In the case of the miR-497~195 cluster, editing of miR-195 led to a significant decrease in the expression of the other miRNA in the cluster, miR-497a. Although no gene editing was detected in the miR-497a genomic locus, computational simulation revealed alteration in the three dimensional structure of the pri miR-497~195 that may affect its processing. In cluster miR- 143~145 our results imply a feed-forward regulation, although structural changes cannot be ruled out. Furthermore, in the miR-17~92 and miR-106~25 clusters no interdependency in miRNA expression was observed. Our findings suggest that CRISPR/Cas9 is a powerful gene editing tool that can uncover novel mechanisms of clustered miRNA regulation and function
The GRAVITY metrology system: modeling a metrology in optical fibers
GRAVITY is the second generation VLT Interferometer (VLTI) instrument for
high-precision narrow-angle astrometry and phase-referenced interferometric
imaging. The laser metrology system of GRAVITY is at the heart of its
astrometric mode, which must measure the distance of 2 stars with a precision
of 10 micro-arcseconds. This means the metrology has to measure the optical
path difference between the two beam combiners of GRAVITY to a level of 5 nm.
The metrology design presents some non-common paths that have consequently to
be stable at a level of 1 nm. Otherwise they would impact the performance of
GRAVITY. The various tests we made in the past on the prototype give us hints
on the components responsible for this error, and on their respective
contribution to the total error. It is however difficult to assess their exact
origin from only OPD measurements, and therefore, to propose a solution to this
problem. In this paper, we present the results of a semi-empirical modeling of
the fibered metrology system, relying on theoretical basis, as well as on
characterisations of key components. The modeling of the metrology system
regarding various effects, e.g., temperature, waveguide heating or mechanical
stress, will help us to understand how the metrology behave. The goals of this
modeling are to 1) model the test set-ups and reproduce the measurements (as a
validation of the modeling), 2) determine the origin of the non-common path
errors, and 3) propose modifications to the current metrology design to reach
the required 1nm stability.Comment: 20 pages, 19 figures. Proceeding of SPIE 9146 "Optical and Infrared
Interferometry IV
Crispr/Cas9 gene editing reveals novel tertiary constraints in clustered mirna processing
MicroRNAs (miRNAs) play an important role in the cellular function. They often form families, with members sharing high sequence homology, a property that hampers miRNA research as there is a lack of elegant tools for specific miRNA manipulation
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