15,751 research outputs found
Assessing Developmental Assessment in Community Colleges
Placement exams are high-stakes assessments that determine many students' college trajectories. The majority of community colleges use placement examsâmost often the ACCUPLACER, developed by the College Board, or the COMPASS, developed by ACT, Inc.âto sort students into college-level or developmental education courses in math, reading, and sometimes writing. More than half of entering students at community colleges are placed into developmental education in at least one subject as a result. But the evidence on the predictive validity of these tests is not as strong as many might assume, given the stakes involvedâand recent research fails to find evidence that the resulting placements into remediation improve student outcomes. While this has spurred debate about the content and delivery of remedial coursework, it is possible that the assessment process itself may be broken; the debate about remediation policy is incomplete without a fuller understanding of the role of assessment. This Brief examines the role of developmental assessment, the validity of the most common assessments currently in use, and emerging directions in assessment policy and practice. Alternative methods of assessmentâparticularly those involving multiple measures of student preparednessâseem to have the potential to improve student outcomes, but more research is needed to determine what type of change in assessment and placement policy might improve persistence and graduation rates. The Brief concludes with a discussion of implications for policy and research
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Pyrimidine Biosynthesis in the Genus Streptomyces : Characterization of Aspartate Transcarbamoylase and Its Interaction with Other Pyrimidine Enzymes
Aspartate transcarbamoylase (ATCase) of Streptomyces was characterized and its interaction with other pyrimidine enzymes explored
One-Loop Renormalization of Higher-Derivative 2D Dilaton Gravity
A theory of higher-derivative 2D dilaton gravity which has its roots in the
massive higher-spin mode dynamics of string theory is suggested. The
divergences of the effective action to one-loop are calculated, both in the
covariant and in the conformal gauge. Some technical problems which appear in
the calculations are discussed. An interpretation of the theory as a particular
D=2 higher-derivative -model is given. For a specific case of
higher-derivative 2D dilaton gravity, which is one loop multiplicatively
renormalizable, static configurations corresponding to black holes are shown to
exist.Comment: 12 pages, LaTeX fil
Motif Discovery through Predictive Modeling of Gene Regulation
We present MEDUSA, an integrative method for learning motif models of
transcription factor binding sites by incorporating promoter sequence and gene
expression data. We use a modern large-margin machine learning approach, based
on boosting, to enable feature selection from the high-dimensional search space
of candidate binding sequences while avoiding overfitting. At each iteration of
the algorithm, MEDUSA builds a motif model whose presence in the promoter
region of a gene, coupled with activity of a regulator in an experiment, is
predictive of differential expression. In this way, we learn motifs that are
functional and predictive of regulatory response rather than motifs that are
simply overrepresented in promoter sequences. Moreover, MEDUSA produces a model
of the transcriptional control logic that can predict the expression of any
gene in the organism, given the sequence of the promoter region of the target
gene and the expression state of a set of known or putative transcription
factors and signaling molecules. Each motif model is either a -length
sequence, a dimer, or a PSSM that is built by agglomerative probabilistic
clustering of sequences with similar boosting loss. By applying MEDUSA to a set
of environmental stress response expression data in yeast, we learn motifs
whose ability to predict differential expression of target genes outperforms
motifs from the TRANSFAC dataset and from a previously published candidate set
of PSSMs. We also show that MEDUSA retrieves many experimentally confirmed
binding sites associated with environmental stress response from the
literature.Comment: RECOMB 200
Dielectrophoresis of nanocolloids: a molecular dynamics study
Dielectrophoresis (DEP), the motion of polarizable particles in non-uniform
electric fields, has become an important tool for the transport, separation,
and characterization of microparticles in biomedical and nanoelectronics
research. In this article we present, to our knowledge, the first molecular
dynamics simulations of DEP of nanometer-sized colloidal particles. We
introduce a simplified model for polarizable nanoparticles, consisting of a
large charged macroion and oppositely charged microions, in an explicit
solvent. The model is then used to study DEP motion of the particle at
different combinations of temperature and electric field strength. In accord
with linear response theory, the particle drift velocities are shown to be
proportional to the DEP force. Analysis of the colloid DEP mobility shows a
clear time dependence, demonstrating the variation of friction under
non-equilibrium. The time dependence of the mobility further results in an
apparent weak variation of the DEP displacements with temperature
Frequency dispersion reduction and bond conversion on n-type GaAs by in situ surface oxide removal and passivation
The method of surface preparation on n-type GaAs, even with the presence of an amorphous-Si interfacial passivation layer, is shown to be a critical step in the removal of accumulation capacitance frequency dispersion. In situ deposition and analysis techniques were used to study different surface preparations, including NH4OH, Si-flux, and atomic hydrogen exposures, as well as Si passivation depositions prior to in situ atomic layer deposition of Al2O3. AsâO bonding was removed and a bond conversion process with Si deposition is observed. The accumulation capacitance frequency dispersion was removed only when a Si interlayer and a specific surface clean were combined
Association of parenting practices to encourage or discourage physical activity with Hispanic preschool children's objectively measured physical activity
Oral Session - Determinants of physical activity in children and adolescents: no. O.002Conference Theme: Promoting Healthy Eating and Activity WorldwidePURPOSE: Assess the association of parenting practices (PP) to encourage or discourage physical activity (PA) with Hispanic 3-5 year old childrenâs objectively measured PA METHOD: Cross-sectional study of Hispanic parent-child dyads (n= 84) who reported their demographics and frequency of using PP that encourage (structure/encouragement) or discourage (promote inactive transport, promote screen time, psychological control, and safety concerns) child PA using verified scales. Children wore Actigraph GT3X accelerometers recording 15 second epochs for 7 days. Allowing for re-wears âŠpostprin
Psychometrics of new scales of parenting practices to encourage or discourage Hispanic preschool children's physical activity
Conference Theme: Promoting Healthy Eating and activity worldwidePoster - Personal and environmental determinants of physical activity in children and adolescents: abstract P077PURPOSE: Develop and assess the psychometrics of a new instrument for parenting practices (PP) that encourage or discourage physical activity (PA) in Hispanic preschool children. METHOD: Cross--âsectional study of 240 Hispanic parents who reported their demographics and frequency of using PP that encourage (structure and encouragement) or discourage (promoting inactivity, psychological control, safety âŠpostprin
GaAs interfacial self-cleaning by atomic layer deposition
The reduction and removal of surface oxides from GaAs substrates by atomic layer deposition (ALD) of Al2O3 and HfO2 are studied using in situ monochromatic x-ray photoelectron spectroscopy. Using the combination of in situ deposition and analysis techniques, the interfacial "self-cleaning" is shown to be oxidation state dependent as well as metal organic precursor dependent. Thermodynamics, charge balance, and oxygen coordination drive the removal of certain species of surface oxides while allowing others to remain. These factors suggest proper selection of surface treatments and ALD precursors can result in selective interfacial bonding arrangements
The Nature of the Hall Insulator
We have conducted an experimental study of the linear transport properties of
the magnetic-field induced insulating phase which terminates the quantum Hall
(QH) series in two dimensional electron systems. We found that a direct and
simple relation exists between measurements of the longitudinal resistivity,
, in this insulating phase and in the neighboring QH phase. In
addition, we find that the Hall resistivity, , can be quantized in
the insulating phase. Our results indicate that a close relation exists between
the conduction mechanism in the insulator and in the QH liquid.Comment: RevTeX, 4 pages, 4 figure
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