1,761 research outputs found
Detection and partial sequence analysis of gastrin mRNA by using an oligodeoxynucleotide probe.
On the relevance of the mathematics curriculum to young people
In this paper we draw upon focus group data from a large study of learner trajectories through 14-19 mathematics education to think about the notion of relevance in the mathematics curriculum. Drawing on data from three socially distanced sites we explore how different emphases on what might be termed practical, process and/or professional forms of relevance affect the experiences and aspirations of learners of mathematics. We consider whether an emphasis on practical relevance in schools serving relatively disadvantaged communities might aid the reproduction of studentsâ social position. This leads us to suggest that a fourth category of curriculum relevance â political relevance â is largely missing from classrooms
A qualitative evidence synthesis of patient perspectives on migraine treatment features and outcomes
TeV Gamma-Ray Sources from a Survey of the Galactic Plane with Milagro
A survey of Galactic gamma-ray sources at a median energy of ~20 TeV has been
performed using the Milagro Gamma Ray Observatory. Eight candidate sources of
TeV emission are detected with pre-trials significance in the
region of Galactic longitude and latitude
. Four of these sources, including the Crab nebula
and the recently published MGRO J2019+37, are observed with significances
after accounting for the trials involved in searching the 3800
square degree region. All four of these sources are also coincident with EGRET
sources. Two of the lower significance sources are coincident with EGRET
sources and one of these sources is Geminga. The other two candidates are in
the Cygnus region of the Galaxy. Several of the sources appear to be spatially
extended. The fluxes of the sources at 20 TeV range from ~25% of the Crab flux
to nearly as bright as the Crab.Comment: Submitted to Ap
Milagro Constraints on Very High Energy Emission from Short Duration Gamma-Ray Bursts
Recent rapid localizations of short, hard gamma-ray bursts (GRBs) by the
Swift and HETE satellites have led to the observation of the first afterglows
and the measurement of the first redshifts from this type of burst. Detection
of >100 GeV counterparts would place powerful constraints on GRB mechanisms.
Seventeen short duration (< 5 s) GRBs detected by satellites occurred within
the field of view of the Milagro gamma-ray observatory between 2000 January and
2006 December. We have searched the Milagro data for >100 GeV counterparts to
these GRBs and find no significant emission correlated with these bursts. Due
to the absorption of high-energy gamma rays by the extragalactic background
light (EBL), detections are only expected for redshifts less than ~0.5. While
most long duration GRBs occur at redshifts higher than 0.5, the opposite is
thought to be true of short GRBs. Lack of a detected VHE signal thus allows
setting meaningful fluence limits. One GRB in the sample (050509b) has a likely
association with a galaxy at a redshift of 0.225, while another (051103) has
been tentatively linked to the nearby galaxy M81. Fluence limits are corrected
for EBL absorption, either using the known measured redshift, or computing the
corresponding absorption for a redshift of 0.1 and 0.5, as well as for the case
of z=0.Comment: Accepted for publication in the Astrophysical Journa
HAT-P-6b: A Hot Jupiter transiting a bright F star
In the ongoing HATNet survey we have detected a giant planet, with radius
1.33 +/- 0.06 RJup and mass 1.06 +/- 0.12 MJup, transiting the bright (V =
10.5) star GSC 03239-00992. The planet is in a circular orbit with period
3.852985 +/- 0.000005 days and mid-transit epoch 2,454,035.67575 +/- 0.00028
(HJD). The parent star is a late F star with mass 1.29 +/- 0.06 Msun, radius
1.46 +/- 0.06 Rsun, Teff ~ 6570 +/- 80 K, [Fe=H] = -0.13 +/- 0.08 and age ~
2.3+/-^{0.5}_{0.7}Gy. With this radius and mass, HAT-P-6b has somewhat larger
radius than theoretically expected. We describe the observations and their
analysis to determine physical properties of the HAT-P-6 system, and briefly
discuss some implications of this finding.Comment: Accepted for publication in ApJL, 5 pages, minor changes compared to
V
The CORALIE survey for southern extra-solar planets. X. A Hot Jupiter orbiting HD73256
Recent radial-velocity measurements obtained with the CORALIE spectrograph on
the 1.2-m Euler Swiss telescope at La Silla unveil the presence of a new
Jovian-mass Hot Jupiter around HD 73256. The 1.85-M_Jup planet moves on an
extremely short-period (P=2.5486 d), quasi-circular orbit. The best Keplerian
orbital solution is presented together with an unsuccessful photometric
planetary-transit search performed with the SAT Danish telescope at La Silla.
Over the time span of the observations, the photometric follow-up of the
candidate has nevertheless revealed a P=14-d photometric periodicity
corresponding to the rotational period of the star. This variation as well as
the radial-velocity jitter around the Keplerian solution are shown to be
related to the fair activity level known for HD 73256.Comment: 7 pages, 7 figures. Accepted in A&
Discovery of Localized Regions of Excess 10-TeV Cosmic Rays
An analysis of 7 years of Milagro data performed on a 10-degree angular scale
has found two localized regions of excess of unknown origin with greater than
12 sigma significance. Both regions are inconsistent with gamma-ray emission
with high confidence. One of the regions has a different energy spectrum than
the isotropic cosmic-ray flux at a level of 4.6 sigma, and it is consistent
with hard spectrum protons with an exponential cutoff, with the most
significant excess at ~10 TeV. Potential causes of these excesses are explored,
but no compelling explanations are found.Comment: Submitted to PhysRevLet
HAT-P-49b: A 1.7 M_J Planet Transiting a Bright 1.5 M_S F-Star
We report the discovery of the transiting extrasolar planet HAT-P-49b. The
planet transits the bright (V = 10.3) slightly evolved F-star HD 340099 with a
mass of 1.54M_S and a radius of 1.83 R_S. HAT-P-49b is orbiting one of the 25
brightest stars to host a transiting planet which makes this a favorable
candidate for detailed follow-up. This system is an especially strong target
for Rossiter- McLaughlin follow-up due to the fast rotation of the host star,
16 km/s. The planetary companion has a period of 2.6915 d, mass of 1.73 M_J and
radius of 1.41 R_J. The planetary characteristics are consistent with that of a
classical hot Jupiter but we note that this is the fourth most massive star to
host a transiting planet with both M_p and R_p well determined.Comment: Accepted to the Astronomical Journa
The Intrinsic Origin of Spin Echoes in Dipolar Solids Generated by Strong Pi Pulses
In spectroscopy, it is conventional to treat pulses much stronger than the
linewidth as delta-functions. In NMR, this assumption leads to the prediction
that pi pulses do not refocus the dipolar coupling. However, NMR spin echo
measurements in dipolar solids defy these conventional expectations when more
than one pi pulse is used. Observed effects include a long tail in the CPMG
echo train for short delays between pi pulses, an even-odd asymmetry in the
echo amplitudes for long delays, an unusual fingerprint pattern for
intermediate delays, and a strong sensitivity to pi-pulse phase. Experiments
that set limits on possible extrinsic causes for the phenomena are reported. We
find that the action of the system's internal Hamiltonian during any real pulse
is sufficient to cause the effects. Exact numerical calculations, combined with
average Hamiltonian theory, identify novel terms that are sensitive to
parameters such as pulse phase, dipolar coupling, and system size.
Visualization of the entire density matrix shows a unique flow of quantum
coherence from non-observable to observable channels when applying repeated pi
pulses.Comment: 24 pages, 27 figures. Revised from helpful referee comments. Added
new Table IV, new paragraphs on pages 3 and 1
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