12,576 research outputs found
Exploring the Relationship between K-8 Prospective Teachers’ Algebraic Thinking Proficiency and the Questions They Pose during Diagnostic Algebraic Thinking Interviews
In this study, we explored the relationship between prospective teachers’ algebraic thinking and the questions they posed during one-on-one diagnostic interviews that focused on investigating the algebraic thinking of middle school students. To do so, we evaluated prospective teachers’ algebraic thinking proficiency across 125 algebra-based tasks and we analyzed the characteristics of questions they posed during the interviews. We found that prospective teachers with lower algebraic thinking proficiency did not ask any probing questions. Instead, they either posed questions that simply accepted and affirmed student responses or posed questions that guided the students toward an answer without probing student thinking. In contrast, prospective teachers with higher algebraic thinking proficiency were able to pose probing questions to investigate student thinking or help students clarify their thinking. However, less than half of their questions were of this probing type. These results suggest that prospective teachers’ algebraic thinking proficiency is related to the types of questions they ask to explore the algebraic thinking of students. Implications for mathematics teacher education are discussed
K-8 Pre-service Teachers’ Algebraic Thinking: Exploring the Habit of Mind Building Rules to Represent Functions
In this study, through the lens of the algebraic habit of mind Building Rules to Represent Functions, we examined 18 pre-service middle school teachers\u27 ability to use algebraic thinking to solve problems. The data revealed that pre-service teachers\u27 ability to use different features of the habit of mind Building Rules to Represent Functions varied across the features. Significant correlations existed between 8 pairs of the features. The ability to justify a rule was the weakest of the seven features and it was correlated with the ability to chunk information. Implications for mathematics teacher education are discussed
How an improved implementation of H2 self-shielding influences the formation of massive stars and black holes
High redshift quasars at z>6 have masses up to ~ M. One of the
pathways to their formation includes direct collapse of gas, forming a
supermassive star, precursor of the black hole seed. The conditions for direct
collapse are more easily achievable in metal-free haloes, where atomic hydrogen
cooling operates and molecular hydrogen (H2) formation is inhibited by a strong
external UV flux. Above a certain value of UV flux (J_crit), the gas in a halo
collapses isothermally at ~ K and provides the conditions for
supermassive star formation. However, H2 can self-shield, reducing the effect
of photodissociation. So far, most numerical studies used the local Jeans
length to calculate the column densities for self-shielding. We implement an
improved method for the determination of column densities in 3D simulations and
analyse its effect on the value of J_crit. This new method captures the gas
geometry and velocity field and enables us to properly determine the
direction-dependent self-shielding factor of H2 against photodissociating
radiation. We find a value of J_crit that is a factor of two smaller than with
the Jeans approach (~2000 J_21 vs. ~4000 J_21). The main reason for this
difference is the strong directional dependence of the H2 column density. With
this lower value of J_crit, the number of haloes exposed to a flux >J_crit is
larger by more than an order of magnitude compared to previous studies. This
may translate into a similar enhancement in the predicted number density of
black hole seeds.Comment: 14 pages, 12 figures, published in MNRA
Study of Xenopus orthologs of novel genes expressed in the mouse AVE
info:eu-repo/semantics/publishedVersio
Open charm meson production at LHC
We discuss charm production at the LHC. The production of single
pairs is calculated in the -factorization approach. We use
Kimber-Martin-Ryskin unintegrated gluon distributions in the proton. The
hadronization is included with the help of Peterson fragmentation functions.
Transverse momentum and pseudorapidity distributions of charmed mesons are
presented and compared to recent results of the ALICE, LHCb and ATLAS
collaborations. Furthermore we discuss production of two pairs of
within a simple formalism of double-parton scattering (DPS). Surprisingly large
cross sections, comparable to single-parton scattering (SPS), are predicted for
LHC energies. We discuss perspectives how to identify the double scattering
contribution. We predict much larger cross section for large rapidity distance
between charm quarks from different hard parton scatterings compared to single
scattering.Comment: 5 pages, 4 figures, talk given by R. Maciula at the MESON2012 - 12th
International Workshop on Meson Production, Properties and Interaction, 31
May - 5 June 2012, Krakow, Polan
Audiovisual narratives about the case Spain’s stolen babies
The critical discourse analysis is the tool used in this article, to study how audiovisual media have constructed mental representation about the historical facts occurred in Spain between the final stage of the Spanish Civil War (1936–1939) and the late 1980s: the theft of newborn babies. The State has failed in an attempt to establish policies that support truth, justice and reparation as it has been recalled by United Nations experts to the Government of Spain, and the reports and documentaries have become vehicles to capture and recover memories. Our objective is to analyze how this collective awareness has been realized and the contribution of reports and documentaries. Our results show that the Spanish television channels silence the Francoist context to depict the thefts as the product of economical mobs focused on child trafficking. The international channels, however, put the origin of the dictatorship at the center of the discourse
Semiclassical treatment of fusion processes in collisions of weakly bound nuclei
We describe a semiclassical treatment of nuclear fusion reactions involving
weakly bound nuclei. In this treatment, the complete fusion probabilities are
approximated by products of two factors: a tunneling probability and the
probability that the system is in its ground state at the strong absorption
radius. We investigate the validity of the method in a schematic two-channel
application, where the channels in the continuum are represented by a single
resonant state. Comparisons with full coupled-channels calculations are
performed. The agreement between semiclassical and quantal calculations isquite
good, suggesting that the procedure may be extended to more sophisticated
discretizations of the continuum.Comment: 11 pages, 5 figure
Translocating the blood-brain barrier using electrostatics
Copyright © 2012 Ribeiro,Domingues,
Freire,Santos and Castanho. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.Mammalian cell membranes regulate homeostasis, protein activity, and cell signaling. The charge at the membrane surface has been correlated with these key events. Although mammalian cells are known to be slightly anionic, quantitative information on the membrane charge and the importance of electrostatic interactions in pharmacokinetics and pharmacodynamics remain elusive. Recently, we reported for the first time that brain endothelial cells (EC) are more negatively charged than human umbilical cord cells, using zeta-potential measurements by dynamic light scattering. Here, we hypothesize that anionicity is a key feature of the blood-brain barrier (BBB) and contributes to select which compounds cross into the brain. For the sake of comparison, we also studied the membrane surface charge of blood components—red blood cells (RBC), platelets, and peripheral blood mononuclear cells (PBMC).To further quantitatively correlate the negative zeta-potential values with membrane charge density, model membranes with different percentages of anionic lipids were also evaluated. From all the cells tested, brain cell membranes are the most anionic and those having their lipids mostly exposed, which explains why lipophilic cationic compounds are more prone to cross the blood-brain barrier.Fundação para a Ciência e Tecnologia — Ministério da Educação e Ciência (FCT-MEC, Portugal) is acknowledged for funding (including fellowships SFRH/BD/42158/2007 to Marta M.B. Ribeiro, SFRH/BD/41750/2007 to Marco M. Domingues and SFRH/BD/70423/2010 to João M. Freire) and project PTDC/QUI-BIQ/119509/2010. Marie Curie Industry-Academia Partnerships and Pathways (European Commission) is also acknowledged for funding (FP7-PEOPLE-2007-3-1-IAPP, Project 230654)
Compact massive objects in Virgo galaxies: the black hole population
We investigate the distribution of massive black holes (MBHs) in the Virgo
cluster. Observations suggest that AGN activity is widespread in massive
galaxies (M>1e10 solar masses), while at lower galaxy masses star clusters are
more abundant, which might imply a limited presence of central black holes in
these galaxy-mass regimes. We explore if this possible threshold in MBH
hosting, is linked to nature, nurture, or a mixture of both. The nature
scenario arises naturally in hierarchical cosmologies, as MBH formation
mechanisms typically are efficient in biased systems, which would later evolve
into massive galaxies. Nurture, in the guise of MBH ejections following MBH
mergers, provides an additional mechanism that is more effective for low mass,
satellite galaxies. The combination of inefficient formation, and lower
retention of MBHs, leads to the natural explanation of the distribution of
compact massive ob jects in Virgo galaxies. If MBHs arrive to the correlation
with the host mass and velocity dispersion during merger-triggered accretion
episodes, sustained tidal stripping of the host galaxies creates a population
of MBHs which lie above the expected scaling between the holes and their host
mass, suggesting a possible environmental dependence.Comment: MNRAS letter
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