1,896 research outputs found
Initial Scientific Results from Phase-Referenced Astrometry of Sub-Arcsecond Binaries
The Palomar Testbed Interferometer has observed several binary star systems
whose separations fall between the interferometric coherence length (a few
hundredths of an arcsecond) and the typical atmospheric seeing limit of one
arcsecond. Using phase-referencing techniques we measure the relative
separations of the systems to precisions of a few tens of micro-arcseconds. We
present the first scientific results of these observations, including the
astrometric detection of the faint third stellar component of the kappa Pegasi
system.Comment: 8 pages, 5 figures. To appear in SPIE conference proceedings volume
5491, "New Frontiers in Stellar Interferometery
Search versus Search for Collapsing Electoral Control Types
Electoral control types are ways of trying to change the outcome of elections
by altering aspects of their composition and structure [BTT92]. We say two
compatible (i.e., having the same input types) control types that are about the
same election system E form a collapsing pair if for every possible input
(which typically consists of a candidate set, a vote set, a focus candidate,
and sometimes other parameters related to the nature of the attempted
alteration), either both or neither of the attempted attacks can be
successfully carried out [HHM20]. For each of the seven general (i.e., holding
for all election systems) electoral control type collapsing pairs found by
Hemaspaandra, Hemaspaandra, and Menton [HHM20] and for each of the additional
electoral control type collapsing pairs of Carleton et al. [CCH+ 22] for veto
and approval (and many other election systems in light of that paper's Theorems
3.6 and 3.9), both members of the collapsing pair have the same complexity
since as sets they are the same set. However, having the same complexity (as
sets) is not enough to guarantee that as search problems they have the same
complexity. In this paper, we explore the relationships between the search
versions of collapsing pairs. For each of the collapsing pairs of Hemaspaandra,
Hemaspaandra, and Menton [HHM20] and Carleton et al. [CCH+ 22], we prove that
the pair's members' search-version complexities are polynomially related (given
access, for cases when the winner problem itself is not in polynomial time, to
an oracle for the winner problem). Beyond that, we give efficient reductions
that from a solution to one compute a solution to the other. For the concrete
systems plurality, veto, and approval, we completely determine which of their
(due to our results) polynomially-related collapsing search-problem pairs are
polynomial-time computable and which are NP-hard.Comment: The metadata's abstract is abridged due to arXiv.org's
abstract-length limit. The paper itself has the unabridged (i.e., full)
abstrac
Separating and Collapsing Electoral Control Types
[HHM20] discovered, for 7 pairs (C,D) of seemingly distinct standard
electoral control types, that C and D are identical: For each input I and each
election system, I is a Yes instance of both C and D, or of neither.
Surprisingly this had gone undetected, even as the field was score-carding how
many std. control types election systems were resistant to; various "different"
cells on such score cards were, unknowingly, duplicate effort on the same
issue. This naturally raises the worry that other pairs of control types are
also identical, and so work still is being needlessly duplicated.
We determine, for all std. control types, which pairs are, for elections
whose votes are linear orderings of the candidates, always identical. We show
that no identical control pairs exist beyond the known 7. We for 3 central
election systems determine which control pairs are identical ("collapse") with
respect to those systems, and we explore containment/incomparability
relationships between control pairs. For approval voting, which has a different
"type" for its votes, [HHM20]'s 7 collapses still hold. But we find 14
additional collapses that hold for approval voting but not for some election
systems whose votes are linear orderings. We find 1 additional collapse for
veto and none for plurality. We prove that each of the 3 election systems
mentioned have no collapses other than those inherited from [HHM20] or added
here. But we show many new containment relationships that hold between some
separating control pairs, and for each separating pair of std. control types
classify its separation in terms of containment (always, and strict on some
inputs) or incomparability.
Our work, for the general case and these 3 important election systems,
clarifies the landscape of the 44 std. control types, for each pair collapsing
or separating them, and also providing finer-grained information on the
separations.Comment: The arXiv.org metadata abstract is an abridged version; please see
the paper for the full abstrac
Causal State Estimation and Heisenberg Uncertainty Principle
The observables of a noisy quantum system can be estimated by appropriately
filtering the records of their continuous measurement. Such filtering is
relevant for state estimation and measurement-based quantum feedback control.
It is therefore imperative that the observables estimated through a causal
filter satisfy the Heisenberg uncertainty principle. In the Markovian setting,
prior work implicitly guarantees this requirement. We show that any causal
estimate of linear observables of a linear, but not necessarily Markovian,
system will satisfy the uncertainty principle. In particular, this is true
irrespective of any feedback control of the system and of where in the feedback
loop -- inside or outside -- the measurement record is accessed. Indeed, causal
estimators using the in-loop measurement record can be as precise as those
using the out-of-loop record. These results clarify the role of causal
estimators to a large class of quantum systems, restores the equanimity of
in-loop and out-of-loop measurements in their estimation and control, and
simplifies future experiments on measurement-based quantum feedback control
Scientific Results from High-precision Astrometry at the Palomar Testbed Interferometer
A new observing mode for the Palomar Testbed Interferometer was developed
in2002-2003 which enables differential astrometry at the level of 20
micro-arcseconds for binary systems with separations of several hundred
milli-arcseconds (mas). This phase-referenced mode is the basis of the Palomar
High-precision Astrometric Search for Exoplanet Systems (PHASES), a search for
giant planets orbiting either the primary or secondary star in fifty binary
systems. We present the first science results from the PHASES search. The
properties of the stars comprising binary systems are determined to high
precision. The mutual inclinations of several hierarchical triple star systems
have been determined. We will present upper limits constraining the the
existence of giant planets in a few of the target systems.Comment: 8 Page
A novel method for radiotherapy patient identification using surface imaging
Performing a procedure on the wrong patient or site is one of the greatest errors that can occur in medicine. The addition of automation has been shown to reduce errors in many processes. In this work we explore the use of an automated patient identification process using optical surface imaging for radiotherapy treatments. Surface imaging uses visible light to align the patient to a reference surface in the treatment room. It is possible to evaluate the similarity between a daily set-up surface image and the reference image using distance to agreement between the points on the two surfaces. The higher the percentage overlapping points within a defined distance, the more similar the surfaces. This similarity metric was used to intercompare 16 left-sided breast patients. The reference surface for each patient was compared to 10 daily treatment surfaces for the same patient, and 10 surfaces from each of the other 15 patients (for a total of 160 comparisons per patient), looking at the percent of points overlapping. For each patient, the minimum same-patient similarity score was higher than the maximum different-patient score. For the group as a whole a threshold was able to classify correct and incorrect patients with high levels of accuracy. A 10-fold cross-validation using linear discriminant analysis gave cross-validation loss of 0.0074. An automated process using surface imaging is a feasible option to provide nonharmful daily patient identification verification using currently available technology
Masses, Luminosities, and Orbital Coplanarities of the mu Orionis Quadruple Star System from PHASES Differential Astrometry
mu Orionis was identified by spectroscopic studies as a quadruple star
system. Seventeen high precision differential astrometry measurements of mu Ori
have been collected by the Palomar High-precision Astrometric Search for
Exoplanet Systems (PHASES). These show both the motion of the long period
binary orbit and short period perturbations superimposed on that caused by each
of the components in the long period system being themselves binaries. The new
measurements enable the orientations of the long period binary and short period
subsystems to be determined. Recent theoretical work predicts the distribution
of relative inclinations between inner and outer orbits of hierarchical systems
to peak near 40 and 140 degrees. The degree of coplanarity of this complex
system is determined, and the angle between the planes of the A-B and Aa-Ab
orbits is found to be 136.7 +/- 8.3 degrees, near the predicted distribution
peak at 140 degrees; this result is discussed in the context of the handful of
systems with established mutual inclinations. The system distance and masses
for each component are obtained from a combined fit of the PHASES astrometry
and archival radial velocity observations. The component masses have relative
precisions of 5% (component Aa), 15% (Ab), and 1.4% (each of Ba and Bb). The
median size of the minor axes of the uncertainty ellipses for the new
measurements is 20 micro-arcseconds. Updated orbits for delta Equulei, kappa
Pegasi, and V819 Herculis are also presented.Comment: 12 Pages, Accepted for publication in A
The orbits of the quadruple star system 88 Tau A from PHASES differential astrometry and radial velocity
We have used high precision differential astrometry from the Palomar
High-precision Astrometric Search for Exoplanet Systems (PHASES) project and
radial velocity measurements covering a time-span of 20 years to determine the
orbital parameters of the 88 Tau A system. 88 Tau is a complex hierarchical
multiple system comprising a total of six stars; we have studied the brightest
4, consisting of two short-period pairs orbiting each other with an 18-year
period. We present the first orbital solution for one of the short-period
pairs, and determine the masses of the components and distance to the system to
the level of a few percent. In addition, our astrometric measurements allow us
to make the first determination of the mutual inclinations of the orbits. We
find that the sub-systems are not coplanar.Comment: Corrected Author Ordering; 12 Pages, Accepted for publication in Ap
Transcriptome profiling of the small intestinal epithelium in germfree versus conventional piglets
<p>Abstract</p> <p>Background</p> <p>To gain insight into host-microbe interactions in a piglet model, a functional genomics approach was used to address the working hypothesis that transcriptionally regulated genes associated with promoting epithelial barrier function are activated as a defensive response to the intestinal microbiota. Cesarean-derived germfree (GF) newborn piglets were colonized with adult swine feces, and villus and crypt epithelial cell transcriptomes from colonized and GF neonatal piglets were compared using laser-capture microdissection and high-density porcine oligonucleotide microarray technology.</p> <p>Results</p> <p>Consistent with our hypothesis, resident microbiota induced the expression of genes contributing to intestinal epithelial cell turnover, mucus biosynthesis, and priming of the immune system. Furthermore, differential expression of genes associated with antigen presentation (pan SLA class I, <it>B2M</it>, <it>TAP1 </it>and <it>TAPBP</it>) demonstrated that microbiota induced immune responses using a distinct regulatory mechanism common for these genes. Specifically, gene network analysis revealed that microbial colonization activated both type I (IFNAR) and type II (IFNGR) interferon receptor mediated signaling cascades leading to enhanced expression of signal transducer and activator of transcription 1 (STAT1), STAT2 and IFN regulatory factor 7 (IRF7) transcription factors and the induction of IFN-inducible genes as a reflection of intestinal epithelial inflammation. In addition, activated RNA expression of NF-kappa-B inhibitor alpha (<it>NFκBIA</it>; a.k.a I-kappa-B-alpha, IKBα) and toll interacting protein (<it>TOLLIP</it>), both inhibitors of inflammation, along with downregulated expression of the immunoregulatory transcription factor GATA binding protein-1 (<it>GATA1</it>) is consistent with the maintenance of intestinal homeostasis.</p> <p>Conclusion</p> <p>This study supports the concept that the intestinal epithelium has evolved to maintain a physiological state of inflammation with respect to continuous microbial exposure, which serves to sustain a tight intestinal barrier while preventing overt inflammatory responses that would compromise barrier function.</p
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