643 research outputs found
Argumentation in school science : Breaking the tradition of authoritative exposition through a pedagogy that promotes discussion and reasoning
The value of argumentation in science education has become internationally recognised and has been the subject of many research studies in recent years. Successful introduction of argumentation activities in learning contexts involves extending teaching goals beyond the understanding of facts and concepts, to include an emphasis on cognitive and metacognitive processes, epistemic criteria and reasoning. The authors focus on the difficulties inherent in shifting a tradition of teaching from one dominated by authoritative exposition to one that is more dialogic, involving small-group discussion based on tasks that stimulate argumentation. The paper builds on previous research on enhancing the quality of argument in school science, to focus on how argumentation activities have been designed, with appropriate strategies, resources and modelling, for pedagogical purposes. The paper analyses design frameworks, their contexts and lesson plans, to evaluate their potential for enhancing reasoning through foregrounding the processes of argumentation. Examples of classroom dialogue where teachers adopt the frameworks/plans are analysed to show how argumentation processes are scaffolded. The analysis shows that several layers of interpretation are needed and these layers need to be aligned for successful implementation. The analysis serves to highlight the potential and limitations of the design frameworks
Overfeeding, Autonomic Regulation and Metabolic Consequences
The autonomic nervous system plays an important role in the regulation of body processes in health and disease. Overfeeding and obesity (a disproportional increase of the fat mass of the body) are often accompanied by alterations in both sympathetic and parasympathetic autonomic functions. The overfeeding-induced changes in autonomic outflow occur with typical symptoms such as adiposity and hyperinsulinemia. There might be a causal relationship between autonomic disturbances and the consequences of overfeeding and obesity. Therefore studies were designed to investigate autonomic functioning in experimentally and genetically hyperphagic rats. Special emphasis was given to the processes that are involved in the regulation of peripheral energy substrate homeostasis. The data revealed that overfeeding is accompanied by increased parasympathetic outflow. Typical indices of vagal activity (such as the cephalic insulin release during food ingestion) were increased in all our rat models for hyperphagia. Overfeeding was also accompanied by increased sympathetic tone, reflected by enhanced baseline plasma norepinephrine (NE) levels in both VMH-lesioned animals and rats rendered obese by hyperalimentation. Plasma levels of NE during exercise were, however, reduced in these two groups of animals. This diminished increase in the exercise-induced NE outflow could be normalized by prior food deprivation. It was concluded from these experiments that overfeeding is associated with increased parasympathetic and sympathetic tone. In models for hyperphagia that display a continuously elevated nutrient intake such as the VMH-lesioned and the overfed rat, this increased sympathetic tone was accompanied by a diminished NE response to exercise. This attenuated outflow of NE was directly related to the size of the fat reserves, indicating that the feedback mechanism from the periphery to the central nervous system is altered in the overfed state.
The Hubble Constant
I review the current state of determinations of the Hubble constant, which
gives the length scale of the Universe by relating the expansion velocity of
objects to their distance. There are two broad categories of measurements. The
first uses individual astrophysical objects which have some property that
allows their intrinsic luminosity or size to be determined, or allows the
determination of their distance by geometric means. The second category
comprises the use of all-sky cosmic microwave background, or correlations
between large samples of galaxies, to determine information about the geometry
of the Universe and hence the Hubble constant, typically in a combination with
other cosmological parameters. Many, but not all, object-based measurements
give values of around 72-74km/s/Mpc , with typical errors of 2-3km/s/Mpc.
This is in mild discrepancy with CMB-based measurements, in particular those
from the Planck satellite, which give values of 67-68km/s/Mpc and typical
errors of 1-2km/s/Mpc. The size of the remaining systematics indicate that
accuracy rather than precision is the remaining problem in a good determination
of the Hubble constant. Whether a discrepancy exists, and whether new physics
is needed to resolve it, depends on details of the systematics of the
object-based methods, and also on the assumptions about other cosmological
parameters and which datasets are combined in the case of the all-sky methods.Comment: Extensively revised and updated since the 2007 version: accepted by
Living Reviews in Relativity as a major (2014) update of LRR 10, 4, 200
La mutaciĂłn de la biblioteca en los inicios del siglo XXI
El papel que las bibliotecas desempeĂąan en la actualidad ha sido cuestionado en
numerosas ocasiones, a causa de la revoluciĂłn tecnolĂłgica a la que se estĂĄ asistiendo,
la cual pondrĂa en amenaza el papel bĂĄsico que hasta ahora tenĂan ĂŠstas. Pero la
realidad es que se observa una tendencia en la que cada vez se construyen mĂĄs
bibliotecas y mĂĄs complejas. Por lo que se torna harto interesante descubrir hacia dĂłnde
camina la arquitectura en este sentido.
A este respecto, se advierte un cambio de paradigma respecto al papel que juega la
biblioteca en la actualidad, provocando a su vez una respuesta en cuanto a la
arquitectura bibliotecaria. Los cambios sociales que se han producido de la mano del
desarrollo de la tecnologĂa, se han visto implicados de forma directa e indirecta en este
cambio de paradigma, presentando los desafĂos a los que se enfrenta la arquitectura
actual.
Debido a la incertidumbre que se presenta de cara a este nuevo periodo, en base a los
constantes cambios que se manifiestan debido a la rĂĄpida evoluciĂłn que sufren las
nuevas tecnologĂas, y de cara a las demandas de esta nueva sociedad, se torna
fundamental la aplicaciĂłn del principio de la flexibilidad en los nuevos espacios
bibliotecarios, pero se rehĂşye de la clĂĄsica soluciĂłn espacial donde el espacio se vuelve
uniforme, sin apenas expresiĂłn plĂĄstica ni variedad.
Por otro lado, se presentan los temidos efectos que la globalizaciĂłn tiene sobre el planeta,
a cualquier escala, y que parecen llevar todo hacia una tendencia universalista. Por lo
que se hace interesante el estudio de la arquitectura bibliotecaria desde diferentes
Ăłpticas a nivel cultural, tomando como referencia la cultura occidental, debido a su
importante papel de cara al origen de este proceso, asĂ como la cultura oriental, definida
prĂĄcticamente como la antĂtesis de ĂŠsta.
Sobre la base de lo planteado, la presente investigaciĂłn, a modo de primera toma de
contacto, ha pretendido abrir un campo de estudio a travĂŠs del cual se puedan
identificar nuevas formas de aplicar la flexibilidad en los espacios bibliotecarios, de cara
a que ĂŠstos no se vuelvan caducos en cuanto al diseĂąo que presentan, ademĂĄs de poner
el causa los procesos de globalizaciĂłn que pretenden reducir la realidad actual, en base
a procesos de homogeneizaciĂłn; por lo que se busca identificar procesos de hibridaciĂłn
en la arquitectura actual, a travĂŠs de los cuales poder identificar si se producen
diferencias entre las distintas culturas, valorando en quĂŠ medida se incluyen las cuestiones
de carĂĄcter local en las obras que representan cada una de estas culturas.
A travĂŠs de la metodologĂa empleada, basada en los estudios de caso individual y en el
anĂĄlisis comparativo de ĂŠstos, se han podido evidenciar lĂneas que muestran esa
evoluciĂłn de la arquitectura actual, en la que se torna evidente la importancia que tiene
la flexibilidad en el nuevo escenario, asĂ como la posibilidad de aplicarla de diversa
manera, ademĂĄs de reconocerse los mencionados procesos de hibridaciĂłn, permitiendo
establecer diferencias entre las dos culturas, desmontando asĂ la ambiciosa visiĂłn de
carĂĄcter unilateral que se tenĂa sobre la globalizaciĂłn.Abstract: The role played by libraries nowadays has been frequently questioned in view of the
technological revolution currently underway, which would seem to threaten the basic
function libraries had up until now. However, what we are actually seeing is a trend in which
a growing number of increasingly complex libraries are being built. Therefore, it is of interest
to take a look at where architecture in this sector is heading.
The truth is, a change can be observed in what is considered to be the model role of
libraries today, which in turn leads to a different response in terms of their architecture. The
social changes that have taken place as a result of developments in technology have
played both a direct and indirect role in such a change of model and represent the
challenges facing current architecture.
Given the uncertainty that exists these days due to the constant changes occurring as a
result of the rapid evolution of new technologies and of societyâs new demands, it has
become essential to build a flexibility component into all new library design concepts,
while shying away from the classic solution of uniform spaces with little plastic variety or
expression.
On the other hand, the effects of globalisation present at all scales of life on this planet
inevitably arise and tend to drive everything towards a common universality. So it is
interesting to study the architecture of libraries from different cultural perspectives, firstly in
Western culture, given the important role it has played in the origin of this process, and
subsequently from the viewpoint of Oriental culture, practically defined as the antithesis of
the former.
On the basis of the above premises, this paper seeks to stand as the initial contact in a line
of research that identifies new ways of applying flexibility into the architecture of libraries
so that they do not become obsolete in terms of their design, as well as identifying the
globalisation processes that seek to reduce current reality through homogenisation
procedures. Therefore, it aims to identify hybridisation processes in current architecture that
serve to ascertain whether distinctions occur between different cultures and to assess the
extent to which local issues find a place in iconic buildings representing each of those
cultures.
By means of the methodology used, based on individual case studies and comparative
analysis of each, certain traits have been revealed that show an evolution in
contemporary architecture, in which greater importance is given in this new scenario to
flexibility and the ability to apply it in different ways, as well as acknowledging the aforementioned
hybridization processes, enabling differences between the two cultures to be
identified and thus any narrow-minded view of globalization as a unilateral phenomenon
to be dismantled
MICE: The muon ionization cooling experiment. Step I: First measurement of emittance with particle physics detectors
Copyright @ 2011 APSThe Muon Ionization Cooling Experiment (MICE) is a strategic R&D project intended to demonstrate the only practical solution to providing high brilliance beams necessary for a neutrino factory or muon collider. MICE is under development at the Rutherford Appleton Laboratory (RAL) in the United Kingdom. It comprises a dedicated beamline to generate a range of input muon emittances and momenta, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. The emittance of the incoming beam will be measured in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in Liquid Hydrogen (LH2) absorbers to RF cavity acceleration. A second spectrometer, identical to the first, and a second muon identification system will measure the outgoing emittance. In the 2010 run at RAL the muon beamline and most detectors were fully commissioned and a first measurement of the emittance of the muon beam with particle physics (time-of-flight) detectors was performed. The analysis of these data was recently completed and is discussed in this paper. Future steps for MICE, where beam emittance and emittance reduction (cooling) are to be measured with greater accuracy, are also presented.This work was supported by NSF grant PHY-0842798
Characteristic Evolution and Matching
I review the development of numerical evolution codes for general relativity
based upon the characteristic initial value problem. Progress in characteristic
evolution is traced from the early stage of 1D feasibility studies to 2D
axisymmetric codes that accurately simulate the oscillations and gravitational
collapse of relativistic stars and to current 3D codes that provide pieces of a
binary black hole spacetime. Cauchy codes have now been successful at
simulating all aspects of the binary black hole problem inside an artificially
constructed outer boundary. A prime application of characteristic evolution is
to extend such simulations to null infinity where the waveform from the binary
inspiral and merger can be unambiguously computed. This has now been
accomplished by Cauchy-characteristic extraction, where data for the
characteristic evolution is supplied by Cauchy data on an extraction worldtube
inside the artificial outer boundary. The ultimate application of
characteristic evolution is to eliminate the role of this outer boundary by
constructing a global solution via Cauchy-characteristic matching. Progress in
this direction is discussed.Comment: New version to appear in Living Reviews 2012. arXiv admin note:
updated version of arXiv:gr-qc/050809
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
Recommended from our members
A Search for Dark Higgs Bosons
Recent astrophysical and terrestrial experiments have motivated the proposal
of a dark sector with GeV-scale gauge boson force carriers and new Higgs
bosons. We present a search for a dark Higgs boson using 516 fb-1 of data
collected with the BABAR detector. We do not observe a significant signal and
we set 90% confidence level upper limits on the product of the Standard
Model-dark sector mixing angle and the dark sector coupling constant.Comment: 7 pages, 5 postscript figures, published version with improved plots
for b/w printin
X-ray emission from the Sombrero galaxy: discrete sources
We present a study of discrete X-ray sources in and around the
bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival
Chandra observations with a total exposure of ~200 ks. With a detection limit
of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30
kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler
et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS
observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray
binaries (LMXBs). We quantify the differential luminosity functions (LFs) for
both the detected GC and field LMXBs, whose power-low indices (~1.1 for the
GC-LF and ~1.6 for field-LF) are consistent with previous studies for
elliptical galaxies. With precise sky positions of the GCs without a detected
X-ray source, we further quantify, through a fluctuation analysis, the GC LF at
fainter luminosities down to 1E35 erg/s. The derived index rules out a
faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent
findings in several elliptical galaxies and the bulge of M31. On the other
hand, the 2-6 keV unresolved emission places a tight constraint on the field
LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101
sources in the halo of Sombrero. The presence of these sources cannot be
interpreted as galactic LMXBs whose spatial distribution empirically follows
the starlight. Their number is also higher than the expected number of cosmic
AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray
surveys. We suggest that either the cosmic X-ray background is unusually high
in the direction of Sombrero, or a distinct population of X-ray sources is
present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres
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