1,512 research outputs found
Tanaka formula and local time for a class of interacting branching measure-valued diffusions
We construct superprocesses with dependent spatial motion (SDSMs) in
Euclidean spaces and show that, even when they start at some unbounded initial
positive Radon measure such as Lebesgue measure on , their local times
exist when . A Tanaka formula is also derived
Mediated Motherhood: Discourse and Maternal Identity in the Digital Age
The ubiquity of the smartphone is both celebrated and contested, since the possibility of constant connectivity is seen as simultaneously inviting and exciting on the one hand, and demanding and burdensome on the other. This thesis uses discourse analysis to analyze a television interview and an online comment forum to shed light on the ways in which experts and mothers talk about the impacts of technology on family interaction and parenting practices. I consider how both experts and parents discursively construct the family-technology relationship by analyzing how parents communicate about technology use (both their own and their children\u27s), the emotional and practical elements of decision-making regarding technology and how these reveal ideologies about the impact of technology on parenting. My primary findings support a body of research that indicates that a mention of parenting in general can be interpreted to implicate mothers specifically. As such, the conversation about the relationship between parenting and technology is constrained by cultural ideologies about maternal responsibility for the care of children and philosophies about the affordances of technology, and entangled with questions of access and class. All of this influences how experts and parents negotiate their identities and work to position themselves as competent on each of these fronts
On the Stability of Oscillatory Pipe Flows
The linear stability of pure oscillatory pipe flow is investigated by solving the linearized disturbance equations as an initial value problem. The importance of the initial conditions on transient dynamics of the flow is analyzed. It is shown that transient growth can play an important role in the development of flow instability. The accuracy of the quasi-steady assumption is assessed. It is shown that the growth rates obtained with this assumption deviate considerably from the results obtained with a direct numerical solution of the linearized initial value problem
Genetic variation in the Epacris tasmanica complex (Epacridaceae).
RAPD (random amplified polymorphic DNA) markers were used to delimit species in the Epacris tasmanica complex (Epacridaceae) collected from various locations in Tasmania, Australia. The RAPD analysis placed morphologically similar taxa located closely geographically into discrete clusters. However, geographically distant populations of morphometrically similar taxa, such as the southern and northern Tasmanian populations of E. virgata and E. tasmanica, were less closely related to each other than those taxa classified as different species. The most geographically remote population (E. glabella [Serpentine Hill]) shared the least genetic similarities with the other taxa. The genetic information obtained from this study reinforces some previous morphometric data used to delimit species in the E. tasmanica complex. Furthermore, the strong geographical structure of the genetic variation is consistent with a model in which gene flow between populations is limited
Magnetic Field Structure around Low-Mass Class 0 Protostars: B335, L1527 and IC348-SMM2
We report new 350 micron polarization observations of the thermal dust
emission from the cores surrounding the low-mass, Class 0 YSOs L1527,
IC348-SMM2 and B335. We have inferred magnetic field directions from these
observations, and have used them together with results in the literature to
determine whether magnetically regulated core-collapse and star-formation
models are consistent with the observations. These models predict a pseudo-disk
with its symmetry axis aligned with the core magnetic field. The models also
predict a magnetic field pinch structure on a scale less than or comparable to
the infall radii for these sources. In addition, if the core magnetic field
aligns (or nearly aligns) the core rotation axis with the magnetic field before
core collapse, then the models predict the alignment (or near alignment) of the
overall pinch field structure with the bipolar outflows in these sources. We
show that if one includes the distorting effects of bipolar outflows on
magnetic fields, then in general the observational results for L1527 and
IC348-SMM2 are consistent with these magnetically regulated models. We can say
the same for B335 only if we assume the distorting effects of the bipolar
outflow on the magnetic fields within the B335 core are much greater than for
L1527 and IC348-SMM2. We show that the energy densities of the outflows in all
three sources are large enough to distort the magnetic fields predicted by
magnetically regulated models.Comment: Accepted for publication in The Astrophysical Journa
Far-infrared polarimetry from the Stratospheric Observatory for Infrared Astronomy
Multi-wavelength imaging polarimetry at far-infrared wavelengths has proven
to be an excellent tool for studying the physical properties of dust, molecular
clouds, and magnetic fields in the interstellar medium. Although these
wavelengths are only observable from airborne or space-based platforms, no
first-generation instrument for the Stratospheric Observatory for Infrared
Astronomy (SOFIA) is presently designed with polarimetric capabilities. We
study several options for upgrading the High-resolution Airborne Wideband
Camera (HAWC) to a sensitive FIR polarimeter. HAWC is a 12 x 32 pixel bolometer
camera designed to cover the 53 - 215 micron spectral range in 4 colors, all at
diffraction-limited resolution (5 - 21 arcsec). Upgrade options include: (1) an
external set of optics which modulates the polarization state of the incoming
radiation before entering the cryostat window; (2) internal polarizing optics;
and (3) a replacement of the current detector array with two state-of-the-art
superconducting bolometer arrays, an upgrade of the HAWC camera as well as
polarimeter. We discuss a range of science studies which will be possible with
these upgrades including magnetic fields in star-forming regions and galaxies
and the wavelength-dependence of polarization.Comment: 12 pages, 5 figure
Characterization of \u3cem\u3eGlomerella\u3c/em\u3e Strains Recovered from Anthracnose Lesions on Common Bean Plants in Brazil
Anthracnose caused by Colletotrichum lindemuthianum is an important disease of common bean, resulting in major economic losses worldwide. Genetic diversity of the C. lindemuthianum population contributes to its ability to adapt rapidly to new sources of host resistance. The origin of this diversity is unknown, but sexual recombination, via the Glomerella teleomorph, is one possibility. This study tested the hypothesis that Glomerella strains that are frequently recovered from bean anthracnose lesions represent the teleomorph of C. lindemuthianum. A large collection of Glomerella isolates could be separated into two groups based on phylogenetic analysis, morphology, and pathogenicity to beans. Both groups were unrelated to C. lindemuthianum. One group clustered with the C. gloeosporioides species complex and produced mild symptoms on bean tissues. The other group, which belonged to a clade that included the cucurbit anthracnose pathogen C. magna, caused no symptoms. Individual ascospores recovered from Glomerella perithecia gave rise to either fertile (perithecial) or infertile (conidial) colonies. Some pairings of perithecial and conidial strains resulted in induced homothallism in the conidial partner, while others led to apparent heterothallic matings. Pairings involving two perithecial, or two conidial, colonies produced neither outcome. Conidia efficiently formed conidial anastomosis tubes (CATs), but ascospores never formed CATs. The Glomerella strains formed appressoria and hyphae on the plant surface, but did not penetrate or form infection structures within the tissues. Their behavior was similar whether the beans were susceptible or resistant to anthracnose. These same Glomerella strains produced thick intracellular hyphae, and eventually acervuli, if host cell death was induced. When Glomerella was co-inoculated with C. lindemuthianum, it readily invaded anthracnose lesions. Thus, the hypothesis was not supported: Glomerella strains from anthracnose lesions do not represent the teleomorphic phase of C. lindemuthianum, and instead appear to be bean epiphytes that opportunistically invade and sporulate in the lesions
Characterizing web pornography consumption from passive measurements
Web pornography represents a large fraction of the Internet traffic, with
thousands of websites and millions of users. Studying web pornography
consumption allows understanding human behaviors and it is crucial for medical
and psychological research. However, given the lack of public data, these works
typically build on surveys, limited by different factors, e.g. unreliable
answers that volunteers may (involuntarily) provide.
In this work, we collect anonymized accesses to pornography websites using
HTTP-level passive traces. Our dataset includes about broadband
subscribers over a period of 3 years. We use it to provide quantitative
information about the interactions of users with pornographic websites,
focusing on time and frequency of use, habits, and trends. We distribute our
anonymized dataset to the community to ease reproducibility and allow further
studies.Comment: Passive and Active Measurements Conference 2019 (PAM 2019). 14 pages,
7 figure
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