2,562 research outputs found
Chiral Extrapolation of Lattice Data for Heavy Baryons
The masses of heavy baryons containing a b quark have been calculated
numerically in lattice QCD with pion masses which are much larger than its
physical value. In the present work we extrapolate these lattice data to the
physical mass of the pion by applying the effective chiral Lagrangian for heavy
baryons, which is invariant under chiral symmetry when the light quark masses
go to zero and heavy quark symmetry when the heavy quark masses go to infinity.
A phenomenological functional form with three parameters, which has the correct
behavior in the chiral limit and appropriate behavior when the pion mass is
large, is proposed to extrapolate the lattice data. It is found that the
extrapolation deviates noticably from the naive linear extrapolation when the
pion mass is smaller than about 500MeV. The mass differences between Sigma_b
and Sigma_b^* and between Sigma_b^{(*)} and Lambda_b are also presented.
Uncertainties arising from both lattice data and our model parameters are
discussed in detail. We also give a comparision of the results in our model
with those obtained in the naive linear extrapolations.Comment: 29 pages, 9 figure
Mid- to Far-Infrared spectroscopy of Sharpless 171
We have collected one-dimensional raster-scan observations of the active
star-forming region Sharpless 171 (S171), a typical HII region-molecular cloud
complex, with the three spectrometers (LWS, SWS, and PHT-S) on board ISO. We
have detected 8 far-infrared fine-structure lines, [OIII] 52um, [NIII] 57um,
[OI] 63um, [OIII] 88um, [NII] 122um, [OI] 146um, [CII] 158um, and [SiII] 35um
together with the far-infrared continuum and the H2 pure rotation transition
(J=5-3) line at 9.66um. The physical properties of each of the three phases
detected, highly-ionized, lowly-ionized and neutral, are investigated through
the far-infrared line and continuum emission. Toward the molecular region,
strong [OI] 146um emission was observed and the [OI] 63um to 146um line ratio
was found to be too small (about 5) compared to the values predicted by current
photodissociation region (PDR) models. We examine possible mechanisms to
account for the small line ratio and conclude that the absorption of the [OI]
63um and the [CII] 158um emission by overlapping PDRs along the line of sight
can account for the observations and that the [OI] 146um emission is the best
diagnostic line for PDRs. We propose a method to estimate the effect of
overlapping clouds using the far-infrared continuum intensity and derive the
physical properties of the PDR. The [SiII] 35um emission is quite strong at
almost all the observed positions. The correlation with [NII] 122um suggests
that the [SiII] emission originates mostly from the ionized gas. The [SiII]
35um to [NII] 122um ratio indicates that silicon of 30% of the solar abundance
must be in the diffuse ionized gas, suggesting that efficient dust destruction
is undergoing in the ionized region.Comment: 15 pages with 15 figures, accepted in Astronomy & Astrophysic
Prospects for local co-governance
British local authorities and their partners are increasingly developing new ways of working together with local communities. The nature of this co-working, however, is complex, multi-faceted and little understood. This article argues for greater clarity of thinking on the topic, by analysing this co-working as a form of political co-governance, and drawing attention in particular to issues of scale and democracy. Using evidence from a study of 43 local authority areas, 16 authorities are identified where co-governance is practised, following three main types of approach: service-influencing, service-delivering and parish council developing. It is concluded that strengthening political co-governance is essential for a healthy democracy
Synthesized grain size distribution in the interstellar medium
We examine a synthetic way of constructing the grain size distribution in the
interstellar medium (ISM). First we formulate a synthetic grain size
distribution composed of three grain size distributions processed with the
following mechanisms that govern the grain size distribution in the Milky Way:
(i) grain growth by accretion and coagulation in dense clouds, (ii) supernova
shock destruction by sputtering in diffuse ISM, and (iii) shattering driven by
turbulence in diffuse ISM. Then, we examine if the observational grain size
distribution in the Milky Way (called MRN) is successfully synthesized or not.
We find that the three components actually synthesize the MRN grain size
distribution in the sense that the deficiency of small grains by (i) and (ii)
is compensated by the production of small grains by (iii). The fraction of each
{contribution} to the total grain processing of (i), (ii), and (iii) (i.e., the
relative importance of the three {contributions} to all grain processing
mechanisms) is 30-50%, 20-40%, and 10-40%, respectively. We also show that the
Milky Way extinction curve is reproduced with the synthetic grain size
distributions.Comment: 10 pages, 6 figures, accepted for publication in Earth, Planets, and
Spac
Florida Association of Teacher Educators Journal
______________________________________________________________________________ This article discusses the findings and implications of a study of eight sixth-and eight eighthgrade teachers and their 628 students. Each teacher was observed six times for a total of 240 minutes. The study focused on 1) how teachers manage their students' behavior and how those management strategies impact teachers' interactions with their students and 2) how these strategies impacted student time-on-task behavior. Data analyses showed that as teacher management behaviors increased student time-on-task decreased and teacher instructional 2 behaviors decreased. The authors discuss ways teacher educators can help candidates develop important classroom management skills. ___________________________________________________________________________
Present‐day motion of the Sierra Nevada block and some tectonic implications for the Basin and Range province, North American Cordillera
Global Positioning System (GPS) data from five sites on the stable interior of the Sierra Nevada block are inverted to describe its angular velocity relative to stable North America. The velocity data for the five sites fit the rigid block model with rms misfits of 0.3 mm/yr (north) and 0.8 mm/yr (east), smaller than independently estimated data uncertainty, indicating that the rigid block model is appropriate. The new Euler vector, 17.0°N, 137.3°W, rotation rate 0.28 degrees per million years, predicts that the block is translating to the northwest, nearly parallel to the plate motion direction, at 13–14 mm/yr, faster than previous estimates. Using the predicted Sierra Nevada block velocity as a kinematic boundary condition and GPS, VLBI and other data from the interior and margins of the Basin and Range, we estimate the velocities of some major boundary zone faults. For a transect approximately perpendicular to plate motion through northern Owens Valley, the eastern California shear zone (western boundary of the Basin and Range province) accommodates 11±1 mm/yr of right‐lateral shear primarily on two faults, the Owens Valley‐White Mountain (3±2 mm/yr) and Fish Lake Valley (8±2 mm/yr) fault zones, based on a viscoelastic coupling model that accounts for the effects of the 1872 Owens Valley earthquake and the rheology of the lower crust. Together these two faults, separated by less than 50 km on this transect, define a region of high surface velocity gradient on the eastern boundary of the Sierra Nevada block. The Wasatch Fault zone accommodates less than 3±1 mm/yr of east‐west extension on the eastern boundary of the Basin and Range province. Remaining deformation within the Basin and Range interior is also probably less than 3 mm/yr
Approaching public perceptions of datafication through the lens of inequality: a case study in public service media
In the emerging field of critical data studies, there is increasing acknowledgement that the negative effects of datafication are not experienced equally by all. Research on data and discrimination in particular has highlighted how already socially unequal populations are discriminated against in data-driven systems. Elsewhere, there is growing interest in public perceptions of datafication, amongst academic researchers interested in producing ‘bottom up’ understandings of the new roles of data in society and non-academic stakeholders keen to
establish positive perceptions of data-driven systems. However, research into public perceptions rarely engages with the issue of inequality which is so central in data and discrimination
scholarship. Bringing these two issues together, this paper explores public perceptions of datafication through the lens of inequality, focusing on the relationship between understandings
and feelings within these perceptions. The paper draws on empirical focus group research into how audiences perceive the data practices that signing in to access BBC digital services enable. The paper shows how inequalities relating to age, dis/ability, poverty and their intersections played a role in shaping perceptions and that these social inequalities informed understandings of and feelings about data practices in complex and diverse ways. It concludes with reflections on the significance of these findings for future research and for data-related policy
Expression and regulation of drug transporters in vertebrate neutrophils.
There remains a need to identify novel pro-resolution drugs for treatment of inflammatory disease. To date, there are no neutrophil-specific anti-inflammatory treatments in clinical use, perhaps due to our lack of understanding of how drugs access this complex cell type. Here we present the first comprehensive description and expression of both major classes of drug transporters, SLC and ABC, in resting human blood neutrophils. Moreover, we have studied the expression of these carriers in the tractable model system, the zebrafish (Danio rerio), additionally examining the evolutionary relationship between drug transporters in zebrafish and humans. We anticipate that this will be a valuable resource to the field of inflammation biology and will be an important asset in future anti-inflammatory drug design
Direct Search for Low Mass Dark Matter Particles with CCDs
A direct dark matter search is performed using fully-depleted
high-resistivity CCD detectors . Due to their low electronic readout noise (RMS
~ 7 eV) these devices operate with a very low detection threshold of 40 eV,
making the search for dark matter particles with low masses (~ 5 GeV) possible.
The results of an engineering run performed in a shallow underground site are
presented, demonstrating the potential of this technology in the low mass
region
Time-Resolved Studies of Stick-Slip Friction in Sheared Granular Layers
Sensitive and fast force measurements are performed on sheared granular
layers undergoing stick-slip motion, along with simultaneous imaging. A full
study has been done for spherical particles with a +-20% size distribution.
Stick-slip motion due to repetitive fluidization of the layer occurs for low
driving velocities. Between major slip events, slight creep occurs that is
variable from one event to the next. The effects of changing the stiffness k
and velocity V of the driving system are studied in detail. The stick-slip
motion is almost periodic for spherical particles over a wide range of
parameters, but becomes irregular when k is large and V is relatively small. At
larger V, the motion becomes smoother and is affected by the inertia of the
upper plate bounding the layer. Measurements of the period T and amplitude A of
the relative motion are presented as a function of V. At a critical value Vc, a
transition to continuous sliding motion occurs that is discontinuous for k not
too large. The time dependence of the instantaneous velocity of the upper plate
and the frictional force produced by the granular layer are determined within
individual slipping events. The force is a multi-valued function of the
instantaneous velocity, with pronounced hysteresis and a sudden drop prior to
resticking. Measurements of vertical displacement reveal a small dilation of
the material (about one tenth of the mean particle size in a layer 20 particles
deep) associated with each slip event. Finally, optical imaging reveals that
localized microscopic rearrangements precede (and follow) each slip event. The
behavior of smooth particles is contrasted with that of rough particles.Comment: 20, pages, 17 figures, to appear in Phys. Rev.
- …