14,111 research outputs found
Studies concerning sperm transfer in some higher diptera
Imperial Users onl
Upper-division student difficulties with Separation of Variables
Separation of variables can be a powerful technique for solving many of the
partial differential equations that arise in physics contexts. Upper-division
physics students encounter this technique in multiple topical areas including
electrostatics and quantum mechanics. To better understand the difficulties
students encounter when utilizing the separation of variables technique, we
examined students' responses to midterm exam questions and a standardized
conceptual assessment, and conducted think-aloud, problem-solving interviews.
Our analysis was guided by an analytical framework that focuses on how students
activate, construct, execute, and reflect on the separation of variables
technique when solving physics problems. Here we focus on student difficulties
with separation of variables as a technique to solve Laplace's equation in both
Cartesian and spherical coordinates in the context of junior-level
electrostatics. Challenges include: recognizing when separation of variables is
the appropriate tool; recalling/justifying the separated form of the potential
and the need for the infinite sum; identifying implicit boundary conditions;
and spontaneously reflecting on their solutions. Moreover, the type and
frequency of errors was often different for SoV problems in Cartesian and
spherical geometries. We also briefly discuss implication of these our findings
for instruction.Comment: 13 pages, 3 figures, submitted to Phys. Rev. ST-PE
Multiple-choice Assessment for Upper-division Electricity and Magnetism
The Colorado Upper-division Electrostatics (CUE) diagnostic was designed as
an open-ended assessment in order to capture elements of student reasoning in
upper-division electrostatics. The diagnostic has been given for many semesters
at several universities resulting in an extensive database of CUE responses. To
increase the utility and scalability of the assessment, we used this database
along with research on students' difficulties to create a multiple-choice
version. The new version explores the viability of a novel test format where
students select multiple responses and can receive partial credit based on the
accuracy and consistency of their selections. This format was selected with the
goal of preserving insights afforded by the open-ended format while exploiting
the logistical advantages of a multiple-choice assessment. Here, we present
examples of the questions and scoring of the multiple-choice CUE as well as
initial analysis of the test's validity, item difficulty, discrimination, and
overall consistency with the open-ended version.Comment: 4 pages, 3 figures, accepted 2013 Physics Education Research
Conference proceeding
Assessing Student Learning in Middle-Division Classical Mechanics/Math Methods
Reliable and validated assessments of introductory physics have been
instrumental in driving curricular and pedagogical reforms that lead to
improved student learning. As part of an effort to systematically improve our
sophomore-level Classical Mechanics and Math Methods course (CM 1) at CU
Boulder, we are developing a tool to assess student learning of CM 1 concepts
in the upper-division. The Colorado Classical Mechanics/Math Methods Instrument
(CCMI) builds on faculty-consensus learning goals and systematic observations
of student difficulties. The result is a 9-question open-ended post-test that
probes student learning in the first half of a two-semester classical mechanics
/ math methods sequence. In this paper, we describe the design and development
of this instrument, its validation, and measurements made in classes at CU
Boulder.Comment: 4 pages, 3 figures, 1 table; submitted to 2013 Proceedings of the
Physics Education Research Conferenc
Oviposition and development in the glass frog Hyalinobatrachium orientale (Anura: Centrolenidae)
Oviposition and development in the glass frog Hyalinobatrachium orientale (Anura: Centrolenidae). Oviposition and external embryonic developmental features are described in the Tobago glass frog, Hyalinobatrachium orientale. Egg clutches are nearly always laid on the undersides of leaves (one exception); usually leaves of Heliconia sp. are used, but Philodendron and palms may be used in the absence of Heliconia. Clutches contain 28.0 ± 5.3 eggs (mean ± SD) and eggs are 1.86 ± 0.11 mm in diameter. The behavior of one amplectant pair was followed for more than five hours; the pair rotated several times around a small area of the leaf depositing eggs in a tight spiral formation. External embryonic features were observed by scanning electron microscopy. Surface ciliation is extensive up to the time of hatching when it is lost; external gills are short and a cement gland is absent. Hatching gland cells were detectable on the anterodorsal surface of the head from Day 4 after deposition and persisted until at least Day 10, and hatching occurred between Days 9 and 16. During this period, progressive development in tail length, surface pigmentation, intestinal coiling, and oral disc features was observed. Post-hatching larvae reared for six weeks grew 37% in length and tripled in weight, but remained at Gosner Stage 25
Effects of Neutron Spatial Distributions on Atomic Parity Nonconservation in Cesium
We have examined modifications to the nuclear weak charge due to small
differences between the spatial distributions of neutrons and protons in the Cs
nucleus. We derive approximate formulae to estimate the value and uncertainty
of this modification based only on nuclear rms neutron and proton radii.
Present uncertainties in neutron distributions in Cs are difficult to quantify,
but we conclude that they should not be neglected when using atomic parity
nonconservation experiments as a means to test the Standard Model.Comment: 5 pages, RevTeX, slightly revised, one figure adde
Validation and analysis of the coupled multiple response Colorado upper-division electrostatics (CUE) diagnostic
Standardized conceptual assessment represents a widely-used tool for
educational researchers interested in student learning within the standard
undergraduate physics curriculum. For example, these assessments are often used
to measure student learning across educational contexts and instructional
strategies. However, to support the large-scale implementation often required
for cross-institutional testing, it is necessary for these instruments to have
question formats that facilitate easy grading. Previously, we created a
multiple-response version of an existing, validated, upper-division
electrostatics diagnostic with the goal of increasing the instrument's
potential for large-scale implementation. Here, we report on the validity and
reliability of this new version as an independent instrument. These findings
establish the validity of the multiple-response version as measured by multiple
test statistics including item difficulty, item discrimination, and internal
consistency. Moreover, we demonstrate that the majority of student responses to
the new version are internally consistent even when they are incorrect, and
provide an example of how the new format can be used to gain insight into
student difficulties with specific content in electrostatics.Comment: 8 pages, 6 figures, submitted to Phys. Rev. ST-PE
The Future of Charge Card Networks
The general-purpose charge card is now ubiquitous and largely taken for granted. Annual charge card volume exceeds $5 trillion worldwide. Within the United States, nearly one billion cards are in use (about eight per household), and more than two billion worldwide. But charge cards, or more specifically, the cooperative networks that serve the largest card systems, Visa and MasterCard, are under legal attack through multiple lawsuits and under regulatory challenge in other countries. We trace in this essay multiple possible future 'scenarios'. This focus on possible futures distinguishes our work from many earlier studies of this subject.
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Dismantling the signposts to public health? NHS data under the Health and Social Care Act 2012
The Health and Social Care Act 2012 will replace the administrative structure of the NHS in England, currently based on the resident populations of defined geographical areas, with one that relates instead to the shifting populations of individuals registered with specific general practices at given points in time.1 This will radically change the longstanding basis for collecting data routinely about the health needs of local populations, making it difficult to monitor the effect of new legislation on the health of the population locally or nationally.2 3 We discuss some of the implications of the act for existing routine data systems and the production of routine statistics that underpin essential NHS functions, including monitoring healthcare provision and ensuring equity of access, allocation of resources, and measurement of outcomes
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