312 research outputs found
Data acquisition system for the MuLan muon lifetime experiment
We describe the data acquisition system for the MuLan muon lifetime
experiment at Paul Scherrer Institute. The system was designed to record muon
decays at rates up to 1 MHz and acquire data at rates up to 60 MB/sec. The
system employed a parallel network of dual-processor machines and repeating
acquisition cycles of deadtime-free time segments in order to reach the design
goals. The system incorporated a versatile scheme for control and diagnostics
and a custom web interface for monitoring experimental conditions.Comment: 19 pages, 8 figures, submitted to Nuclear Instruments and Methods
Innovations in air sampling to detect plant pathogens
Many innovations in the development and use of air sampling devices have occurred in plant pathology since the first description of the Hirst spore trap. These include improvements in capture efficiency at relatively high air-volume collection rates, methods to enhance the ease of sample processing with downstream diagnostic methods and even full automation of sampling, diagnosis and wireless reporting of results. Other innovations have been to mount air samplers on mobile platforms such as UAVs and ground vehicles to allow sampling at different altitudes and locations in a short space of time to identify potential sources and population structure. Geographical Information Systems and the application to a network of samplers can allow a greater prediction of airborne inoculum and dispersal dynamics. This field of technology is now developing quickly as novel diagnostic methods allow increasingly rapid and accurate quantifications of airborne species and genetic traits. Sampling and interpretation of results, particularly action-thresholds, is improved by understanding components of air dispersal and dilution processes and can add greater precision in the application of crop protection products as part of integrated pest and disease management decisions. The applications of air samplers are likely to increase, with much greater adoption by growers or industry support workers to aid in crop protection decisions. The same devices are likely to improve information available for detection of allergens causing hay fever and asthma or provide valuable metadata for regional plant disease dynamics
Boundary Liouville theory at c=1
The c=1 Liouville theory has received some attention recently as the
Euclidean version of an exact rolling tachyon background. In an earlier paper
it was shown that the bulk theory can be identified with the interacting c=1
limit of unitary minimal models. Here we extend the analysis of the c=1-limit
to the boundary problem. Most importantly, we show that the FZZT branes of
Liouville theory give rise to a new 1-parameter family of boundary theories at
c=1. These models share many features with the boundary Sine-Gordon theory, in
particular they possess an open string spectrum with band-gaps of finite width.
We propose explicit formulas for the boundary 2-point function and for the
bulk-boundary operator product expansion in the c=1 boundary Liouville model.
As a by-product of our analysis we also provide a nice geometric interpretation
for ZZ branes and their relation with FZZT branes in the c=1 theory.Comment: 37 pages, 1 figure. Minor error corrected, slight change in result
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Magnetic and thermal properties of 4f-3d ladder-type molecular compounds
We report on the low-temperature magnetic susceptibilities and specific heats
of the isostructural spin-ladder molecular complexes L[M(opba)]_{3\cdot
xDMSOHO, hereafter abbreviated with LM (where L =
La, Gd, Tb, Dy, Ho and M = Cu, Zn). The results show that the Cu containing
complexes (with the exception of LaCu) undergo long range magnetic
order at temperatures below 2 K, and that for GdCu this ordering is
ferromagnetic, whereas for TbCu and DyCu it is probably
antiferromagnetic. The susceptibilities and specific heats of TbCu
and DyCu above have been explained by means of a model
taking into account nearest as well as next-nearest neighbor magnetic
interactions. We show that the intraladder L--Cu interaction is the predominant
one and that it is ferromagnetic for L = Gd, Tb and Dy. For the cases of Tb, Dy
and Ho containing complexes, strong crystal field effects on the magnetic and
thermal properties have to be taken into account. The magnetic coupling between
the (ferromagnetic) ladders is found to be very weak and is probably of dipolar
origin.Comment: 13 pages, 15 figures, submitted to Phys. Rev.
A mouse model featuring tissue-specific deletion of p53 and Brca1 gives rise to mammary tumors with genomic and transcriptomic similarities to human basal-like breast cancer
Purpose and methods: In human basal-like breast cancer, mutations and deletions in TP53 and BRCA1 are frequent oncogenic events. Thus, we interbred mice expressing the CRE-recombinase with mice harboring loxP sites at TP53 and BRCA1 (K14-Cre; p53 f/f Brca1 f/f ) to test the hypothesis that tissue-specific deletion of TP53 and BRCA1 would give rise to tumors reflective of human basal-like breast cancer. Results: In support of our hypothesis, these transgenic mice developed tumors that express basal-like cytokeratins and demonstrated intrinsic gene expression features similar to human basal-like tumors. Array comparative genomic hybridization revealed a striking conservation of copy number alterations between the K14-Cre; p53 f/f Brca1 f/f mouse model and human basal-like breast cancer. Conserved events included MYC amplification, KRAS amplification, and RB1 loss. Microarray analysis demonstrated that these DNA copy number events also led to corresponding changes in signatures of pathway activation including high proliferation due to RB1 loss. K14-Cre; p53 f/f Brca1 f/f also matched human basal-like breast cancer for a propensity to have immune cell infiltrates. Given the long latency of K14-Cre; p53 f/f Brca1 f/f tumors (~ 250 days), we created tumor syngeneic transplant lines, as well as in vitro cell lines, which were tested for sensitivity to carboplatin and paclitaxel. These therapies invoked acute regression, extended overall survival, and resulted in gene expression signatures of an anti-tumor immune response. Conclusion: These findings demonstrate that this model is a valuable preclinical resource for the study of human basal-like breast cancer
Parity nonconserving cold neutron-parahydrogen interactions
Three pion dominated observables of the parity nonconserving interactions
between the cold neutrons and parahydrogen are calculated. The transversely
polarized neutron spin rotation, unpolarized neutron longitudinal polarization,
and photon-asymmetry of the radiative polarized neutron capture are considered.
For the numerical evaluation of the observables, the strong interactions are
taken into account by the Reid93 potential and the parity nonconserving
interactions by the DDH model along with the two-pion exchange.Comment: 17 pages, 2 figure
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
Large-scale Velocity-coherent Filaments in the SEDIGISM Survey: Association with Spiral Arms and Fraction of Dense Gas
Context. Filamentary structures in the interstellar medium are closely related to star formation. Dense gas mass fraction (DGMF) or clump formation efficiency in large-scale filaments possibly determine their hosting star formation activities.
Aims. We aim to automatically identify large-scale filaments, characterize them, investigate their association with Galactic structures, and study their DGMFs.
Methods. We use a modified minimum spanning tree (MST) algorithm to chain parsec-scale 13CO clumps previously extracted from the SEDIGISM (Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) survey. The MST connects nodes in a graph such that the sum of edge lengths is minimum. Modified MST also ensures velocity coherence between nodes, so the identified filaments are coherent in position-position-velocity (PPV) space.
Results. We generate a catalog of 88 large-scale (> 10 pc) filaments in the inner Galactic plane (with −60◦ < l < 18◦ and |b| < 0.5◦). These SEDIGISM filaments are larger and less dense than MST filaments previously identified from the BGPS and ATLASGAL surveys. We find that eight of the filaments run along spiral arms and can be regarded as “bones” of the Milky Way. We also find three bones associated with the Local Spur in PPV space. By compiling 168 large-scale filaments with available DGMF across the Galaxy, an order of magnitude more than previously investigated, we find that DGMFs do not correlate with Galactic location, but bones have higher DGMFs than other filaments
Tides in colliding galaxies
Long tails and streams of stars are the most noticeable upshots of galaxy
collisions. Their origin as gravitational, tidal, disturbances has however been
recognized only less than fifty years ago and more than ten years after their
first observations. This Review describes how the idea of galactic tides
emerged, in particular thanks to the advances in numerical simulations, from
the first ones that included tens of particles to the most sophisticated ones
with tens of millions of them and state-of-the-art hydrodynamical
prescriptions. Theoretical aspects pertaining to the formation of tidal tails
are then presented. The third part of the review turns to observations and
underlines the need for collecting deep multi-wavelength data to tackle the
variety of physical processes exhibited by collisional debris. Tidal tails are
not just stellar structures, but turn out to contain all the components usually
found in galactic disks, in particular atomic / molecular gas and dust. They
host star-forming complexes and are able to form star-clusters or even
second-generation dwarf galaxies. The final part of the review discusses what
tidal tails can tell us (or not) about the structure and content of present-day
galaxies, including their dark components, and explains how tidal tails may be
used to probe the past evolution of galaxies and their mass assembly history.
On-going deep wide-field surveys disclose many new low-surface brightness
structures in the nearby Universe, offering great opportunities for attempting
galactic archeology with tidal tails.Comment: 46 pages, 13 figures, Review to be published in "Tidal effects in
Astronomy and Astrophysics", Lecture Notes in Physics. Comments are most
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