16,408 research outputs found
A Non-Probabilistic Model of Relativised Predictability in Physics
Little effort has been devoted to studying generalised notions or models of
(un)predictability, yet is an important concept throughout physics and plays a
central role in quantum information theory, where key results rely on the
supposed inherent unpredictability of measurement outcomes. In this paper we
continue the programme started in [1] developing a general, non-probabilistic
model of (un)predictability in physics. We present a more refined model that is
capable of studying different degrees of "relativised" unpredictability. This
model is based on the ability for an agent, acting via uniform, effective
means, to predict correctly and reproducibly the outcome of an experiment using
finite information extracted from the environment. We use this model to study
further the degree of unpredictability certified by different quantum
phenomena, showing that quantum complementarity guarantees a form of
relativised unpredictability that is weaker than that guaranteed by
Kochen-Specker-type value indefiniteness. We exemplify further the difference
between certification by complementarity and value indefiniteness by showing
that, unlike value indefiniteness, complementarity is compatible with the
production of computable sequences of bits.Comment: 10 page
Variation in relapse frequency and the transmission potential of Plasmodium vivax malaria
There is substantial variation in the relapse frequency of
Plasmodium vivax malaria, with fast-relapsing strains in
tropical areas, and slow-relapsing strains in temperate areas
with seasonal transmission. We hypothesize that much of the
phenotypic diversity in P. vivax relapses arises from selection
of relapse frequency to optimize transmission potential in a
given environment, in a process similar to the virulence
trade-off hypothesis. We develop mathematical models of P. vivax
transmission and calculate the basic reproduction number R0 to
investigate how transmission potential varies with relapse
frequency and seasonality. In tropical zones with year-round
transmission, transmission potential is optimized at
intermediate relapse frequencies of two to three months:
slower-relapsing strains increase the opportunity for onward
transmission to mosquitoes, but also increase the risk of being
outcompeted by faster-relapsing strains. Seasonality is an
important driver of relapse frequency for temperate strains,
with the time to first relapse predicted to be six to nine
months, coinciding with the duration between seasonal
transmission peaks. We predict that there is a threshold degree
of seasonality, below which fast-relapsing tropical strains are
selected for, and above which slow-relapsing temperate strains
dominate, providing an explanation for the observed global
distribution of relapse phenotypes
Electron-phonon coupling in crystalline organic semiconductors: Microscopic evidence for nonpolaronic charge carriers
We consider electron(hole)-phonon coupling in crystalline organic
semiconductors, using naphthalene for our case study. Employing a
first-principles approach, we compute the changes in the self-consistent
Kohn-Sham potential corresponding to different phonon modes and go on to obtain
the carrier-phonon coupling matrix elements (vertex functions). We then
evaluate perturbatively the quasiparticle spectral residues for electrons at
the bottom of the lowest-unoccupied- (LUMO) and holes at the top of the
highest-occupied (HOMO) band, respectively obtaining and
. Along with the widely accepted notion that the
carrier-phonon coupling strengths in polyacenes decrease with increasing
molecular size, our results provide a strong microscopic evidence for the
previously conjectured nonpolaronic nature of band-like carriers in these
systems.Comment: final, published versio
Detection of CO (2-1) and Radio Continuum Emission from the z = 4.4 QSO BRI 1335-0417
We have detected redshifted CO (2-1) emission at 43 GHz and radio continuum
emission at 1.47 and 4.86 GHz from the z = 4.4 QSO BRI 1335-0417 using the Very
Large Array. The CO data imply optically thick emission from warm (>30 K)
molecular gas with a total mass, M(H_2), of 1.5+/-0.3 x10^{11} M_solar, using
the Galactic gas mass-to-CO luminosity conversion factor. We set an upper limit
to the CO source size of 1.1", and a lower limit of 0.23"x(T_ex/50K)^{-1/2},
where T_ex is the gas excitation temperature. We derive an upper limit to the
dynamical mass of 2x10^{10} x sin^{-2} i M_solar, where i is the disk
inclination angle. To reconcile the gas mass with the dynamical mass requires
either a nearly face-on disk (i < 25deg), or a gas mass-to-CO luminosity
conversion factor significantly lower than the Galactic value. The spectral
energy distribution from the radio to the rest-frame infrared of BRI 1335-0417
is consistent with that expected from a nuclear starburst galaxy, with an
implied massive star formation rate of 2300+/-600 M_solar yr^{-1}.Comment: standard AAS LATEX forma
Limited migration of soluble ionic species in a Siple Dome, Antarctica, ice core
High-resolution (\u3e10 samples a−1) glaciochemical analyses covering the last 110 years from a Siplc Dome, Antarctica, ire core reveal limited migration of certain soluble ionic species (methane sulfonic acid, NO3 − and Mg2+). The observed chemical migration may be due in part to seasonal alternation between less acidic winter (from high sea-salt concentrations) and more acidic summer (from high marine biogenic acid concentrations) layers, common at coastal siles such as Siplc Dome. Exact mechanisms to expla in the migration are unclear, although simple diffusion and gravitational movement are unlikely since new peaks are formed where none previously existed in each case. Initial migration of each species is both shallower and earlier at Siple Dome than at other sites in Antarctica where similar phenomena have been observed, which may be related to the relatively low accumulation rate at Siple Dome (~13.3 cm ice a−1). Migration appears to be limited to either the preceding or following seasonal layer for each species, suggesting that paleoclimatic interpretations based on dala with lower than annual resolution are not likely to be affected
Oscillatory Flows Induced by Microorganisms Swimming in Two-dimensions
We present the first time-resolved measurements of the oscillatory velocity
field induced by swimming unicellular microorganisms. Confinement of the green
alga C. reinhardtii in stabilized thin liquid films allows simultaneous
tracking of cells and tracer particles. The measured velocity field reveals
complex time-dependent flow structures, and scales inversely with distance. The
instantaneous mechanical power generated by the cells is measured from the
velocity fields and peaks at 15 fW. The dissipation per cycle is more than four
times what steady swimming would require.Comment: 4 pages, 4 figure
Unravelling the Mysteries of the Leo Ring: An Absorption Line Study of an Unusual Gas Cloud
Since the 1980's discovery of the large (2x10^9 Msun) intergalactic cloud
known as the Leo Ring, this object has been the center of a lively debate about
its origin. Determining the origin of this object is still important as we
develop a deeper understanding of the accretion and feedback processes that
shape galaxy evolution. We present HST/COS observations of three sightlines
near the Ring, two of which penetrate the high column density neutral hydrogen
gas visible in 21 cm observations of the object. These observations provide the
first direct measurement of the metallicity of the gas in the Ring, an
important clue to its origins. Our best estimate of the metallicity of the ring
is ~10% Zsun, higher than expected for primordial gas but lower than expected
from an interaction. We discuss possible modifications to the interaction and
primordial gas scenarios that would be consistent with this metallicity
measurement.Comment: 11 pages, 7 figures, accepted Ap
Systemic mastocytosis with associated myeloproliferative disease and precursor B lymphoblastic leukaemia with t(13;13)(q12;q22) involving FLT3.
Systemic mastocytoses represent neoplastic proliferations
of mast cells. In about 20% of cases systemic
mastocytoses are accompanied by clonal haematopoietic
non-mast cell-lineage disorders, most commonly myeloid
neoplasms. A case of systemic mastocytosis carrying the
characteristic mutation at codon 816 (D816V) in the KIT
gene of mast cells, with two concurrent accompanying
clonal haematopoietic non-mast cell-lineage disorders,
chronic myeloproliferative disease, unclassifiable and
precursor B lymphoblastic leukaemia is documented. Both
accompanying clonal haematopoietic non-mast cell-lineage
disorders carried the wild-type KIT gene, but had a
novel t(13;13)(q12;q22) involving the FLT3 locus at
13q12. The chronic myeloproliferative disease, unclassifiable
and the precursor B lymphoblastic leukaemia were
cured by syngenous stem cell transplantation, but the
systemic mastocytosis persisted for more than 10 years.
The additional impact of molecular techniques on the
correct diagnosis in haematological malignancies is
highlighted, and evidence is provided that, apart from
internal tandem duplications and mutations, FLT3 can be
activated by translocations
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