1,274 research outputs found
Accelerating Galaxy Winds During the Big Bang of Starbursts
We develop a new method to infer the temporal, geometric, and energetic
properties of galaxy outflows, by combining stellar spectral modeling to infer
starburst ages, and absorption lines to measure velocities. If winds are
accelerated with time during a starburst event, then these two measurements
enable us to solve for the wind radius, similarly to length scales and the
Hubble parameter in Big Bang cosmology. This wind radius is the vital, but
hard-to-constrain parameter in wind physics. We demonstrate the method using
spectra of 87 starburst galaxies at z=0.05-0.44, finding that winds accelerate
throughout the starburst phase and grow to typical radii of ~1 kpc in ~10 Myr.
Mass flow rates increase rapidly with time, and the mass-loading factor exceeds
unity at about 10 Myr - while still being accelerated, the gas will likely
unbind from the local potential and enrich the circumgalactic medium. We model
the mechanical energy available from stellar winds and supernovae, and estimate
that a negligible amount is accounted for in the cool outflow at early times.
However, the energy deposition increases rapidly and ~10% of the budget is
accounted for in the cool flow at 10 Myr, similar to some recent hydrodynamical
simulations. We discuss how this model can be developed, especially for
high-redshift galaxies.Comment: Accepted for publication in MNRAS Letters. 6 pages, 5 figure
Artefact reduction in photoplethysmography
The use of optical techniques in biomedical monitoring and diagnosis is becoming
increasingly widespread, primarily because of the non-invasive nature of optically
derived measurements. Physiological analysis is usually achieved by characterisation
of the spectral or temporal properties of the interaction between light and the
anatomy. Although some optical measurements require complex instrumentation and
protocols, recent technological advances have resulted in robust and compact
equipment that is now used routinely in a multitude of clinical contexts.
Unfortunately, these measurements are inherently sensitive to corruption from
dynamic physical conditions or external sources of light, inducing signal artefact.
Artefact is the primary restriction in the applicability of many optical measurements,
especially for ambulatory monitoring and tele-medicine.
The most widely used optical measurement is photoplethysmography, a technique
that registers dynamic changes in blood volume throughout the peripheral vasculature
and can be used to screen for a number of venous disorders, as well as monitoring the
cardio-vascular pulse wave. Although photoplethysmographic devices are now
incorporated into many patient-monitoring systems, the prevalent application is a
measurement known as pulse oximetry, which utilises spectral analysis of the
peripheral blood to estimate the arterial haernoglobin oxygen saturation. Pulse
oximetry is well established as an early warning for hypoxia and is now mandatory
under anaesthesia in many countries. The problem of artefact is prominent in these
continuous monitoring techniques, where it is often impossible to control the physical
conditions during use.
This thesis investigates the possibility of reducing artefact corruption of
photoplethysmographic signals in real time, using an electronic processing
methodology that is based upon inversion of a physical artefact model. The
consequences of this non-linear artefact reduction technique for subsequent signal
analysis are discussed, culminating in a modified formulation for pulse oximetry that
not only has reduced sensitivity to artefact but also possesses increased generality.
The design and construction of a practical electronic system is then used to explore
both the implementation issues and the scope of this technique. The performance of
artefact reduction obtained is then quantified under realistic experimental conditions,
demonstrating that this methodology is successful in removing or reducing a large
proportion of artefact encountered in clinically relevant situations.
It is concluded that non-linear artefact reduction can be applied to any
photoplethysmographic technology, reducing interpretation inaccuracies that would
otherwise be induced by signal artefact. It is also speculated that this technology
could enable the use of photoplethysmographic systems in applications that are
currently precluded by the inherent severity of artefact
The Role of Narcissistic Hypocrisy in the Development of Accounting Estimates
In an experiment including experienced managers, we investigate how supervisor and subordinate narcissism influence a supervisor’s review of a subordinate’s accounting estimate. While narcissistic supervisors express greater liking for narcissistic subordinates (narcissistic tolerance), they nonetheless reject and revise the accounting estimates of narcissistic subordinates to a greater extent than they reject estimates of non‐narcissistic subordinates (narcissistic hypocrisy), even when doing so inhibits the supervisor’s ability to reach a profit target. Our findings contribute to extant research in accounting and psychology. We demonstrate that narcissistic hypocrisy extends beyond the evaluation of others and alters narcissists’ willingness to rely on other narcissists in a meaningful financial reporting decision. We also find that narcissistic hypocrisy is robust across age, gender, and supervisory experience.RÉSUMÉLe rôle de l’hypocrisie narcissique dans l’élaboration d’estimations comptablesLes auteurs mènent auprès de gestionnaires chevronnés une expérience visant à déterminer en quoi le narcissisme des supérieurs et des subalternes influe sur l’examen auquel les supérieurs soumettent les estimations comptables des subalternes. Bien que les supérieurs narcissiques semblent apprécier davantage les subalternes narcissiques (tolérance narcissique), ils rejettent et révisent néanmoins les estimations des subalternes narcissiques plus souvent qu’ils ne rejettent les estimations des subalternes non narcissiques (hypocrisie narcissique), même lorsque cette décision nuit à leur capacité d’atteindre un objectif de profit. Les résultats de l’étude viennent enrichir les recherches existantes en comptabilité et en psychologie. Les auteurs démontrent que l’hypocrisie narcissique s’étend au‐delà de l’évaluation d’autrui et modifie la mesure dans laquelle les narcissiques sont disposés à s’appuyer sur d’autres narcissiques dans une décision importante en matière d’information financière. Ils observent également que leurs conclusions quant à l’hypocrisie narcissique persistent quels que soient l’-ge, le sexe et l’expérience de supervision.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155911/1/care12552-sup-0001-SupInfo.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155911/2/care12552.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155911/3/care12552_am.pd
Hindbrain Neurons as an Essential Hub in the Neuroanatomically Distributed Control of Energy Balance
This Review highlights the processing and integration performed by hindbrain nuclei, focusing on the inputs received by nucleus tractus solitarius (NTS) neurons. These inputs include vagally mediated gastrointestinal satiation signals, blood-borne energy-related hormonal and nutrient signals, and descending neural signals from the forebrain. We propose that NTS (and hindbrain neurons, more broadly) integrate these multiple energy status signals and issue-output commands controlling the behavioral, autonomic, and endocrine responses that collectively govern energy balance. These hindbrain-mediated controls are neuroanatomically distributed; they involve endemic hindbrain neurons and circuits, hindbrain projections to peripheral circuits, and projections to and from midbrain and forebrain nuclei
Who Sees Corruption? The Bases of Mass Perceptions of Political Corruption in Latin America
The capacity of citizens to see political corruption where it exists and to link such perceptions to evaluations of public officials constitutes an important test of political accountability. Although past research has established that perceived corruption influences political judgments, much less is known regarding the critical prefatory matter of who sees corruption. This article develops a multifaceted theoretical framework regarding the possible bases of perceived corruption. Experiential factors - personal experience and vicarious experience with bribery - mark the starting point for our account. We then incorporate psychological dispositions that may colour judgments about corruption and that may strengthen or weaken the links between experiences and perceptions. Expectations derived from this framework are tested in a series of multi-level models, with data from over 30,000 survey respondents from 17 nations and 84 regions in the Americas
Empirical Estimate of Lyman-alpha Escape Fraction in a Statistical Sample of Lyman-alpha Emitters
The Lyman-alpha (Lya) recombination line is a fundamental tool for galaxy
evolution studies and modern observational cosmology. However, subsequent
interpretations are still prone to a number of uncertainties. Besides numerical
efforts, empirical data are urgently needed for a better understanding of Lya
escape process. We empirically estimate the Lyman-alpha escape fraction
fesc(Lya) in a statistically significant sample of z ~ 0 - 0.3 galaxies in
order to calibrate high-redshift Lyman-alpha observations. An optical
spectroscopic follow-up of a sub-sample of 24 Lyman-alpha emitters (LAEs)
detected by GALEX at z ~ 0.2-0.3, combined with a UV-optical sample of local
starbursts, both with matched apertures, allow us to quantify the dust
extinction through Balmer lines, and to estimate the Lyman-alpha escape
fraction from the Halpha flux corrected for extinction in the framework of the
recombination theory. The global escape fraction of Lyman-alpha radiation spans
nearly the entire range of values, from 0.5 to 100 %, and fesc(Lya) clearly
decreases with increasing nebular dust extinction E(B-V). Several objects show
fesc(Lya) greater than fesc(continuum) which may be an observational evidence
for clumpy ISM geometry or for an aspherical ISM. Selection biases and aperture
size effects may still prevail between z ~ 0.2-0.3 LAEs and local starbursts,
which may explain the difference observed for fesc(Lya).Comment: 4 pages, 2 figures, accepted for publication in Astronomy and
Astrophysic
On the influence of physical galaxy properties on Lyman-alpha escape in star-forming galaxies
[abridged] Among the different observational techniques used to select
high-redshift galaxies, the hydrogen recombination line Lyman-alpha (Lya) is of
particular interest as it gives access to the measurement of cosmological
quantities such as the star formation rate of distant galaxy populations.
However, the interpretation of this line and the calibration of such
observables is still subject to serious uncertainties. Therefore, it important
to understand under what conditions the Lya line can be used as a reliable star
formation diagnostic tool. We use a sample of 24 Lya emitters at z ~ 0.3 with
an optical spectroscopic follow-up to calculate the Lya escape fraction and its
dependency upon different physical properties. We also examine the reliability
of Lya as a star formation rate indicator. We combine these observations with a
compilation of Lya emitters selected at z = 0 - 0.3 to assemble a larger
sample. The Lya escape fraction depends clearly on the dust extinction
following the relation fesc(Lya) = C(Lya) x 10^(-0.4 E(B-V) k(Lya)), but with a
shallower slope than previously reported, with k(Lya) ~ 6.67 and C(Lya) = 0.22.
However, the correlation does not follow the expected curve for a simple dust
attenuation. We explore the various mechanisms than lead to fesc(Lya) values
above the continuum extinction curve, i.e. to an enhancement of the Lya output.
We also observe that the strength of Lya and the escape fraction appear
unrelated to the galaxy metallicity. Regarding the reliability of Lya as a star
formation rate (SFR) indicator, we show that the deviation of SFR(Lya) from the
true SFR (as traced by the UV continuum) is a function of the observed SFR(UV),
which can be seen as the decrease of fesc(Lya) with increasing UV luminosity.
Moreover, we observe a redshift-dependence of this relationship revealing the
underlying evolution of fesc(Lya) with redshift.Comment: 17 pages. Accepted for publicatio
Annexin A2 at the Interface of Actin and Membrane Dynamics: A Focus on Its Roles in Endocytosis and Cell Polarization
Annexins are a family of calcium- and phospholipid-binding proteins found in nearly all eukaryotes. They are structurally highly conserved and have been implicated in a wide range of cellular activities. In this paper, we focus on Annexin A2 (AnxA2). Altered expression of this protein has been identified in a wide variety of cancers, has also been found on the HIV particle, and has been implicated in the maturation of the virus. Recently, it has also been shown to have an important role in the establishment of normal apical polarity in epithelial cells. We synthesize here the known biochemical properties of this protein and the extensive literature concerning its involvement in the endocytic pathway. We stress the importance of AnxA2 as a platform for actin remodeling in the vicinity of dynamic cellular membranes, in the hope that this may shed light on the normal functions of the protein and its contribution to disease
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